Noise aware edge enhancement in a pulsed fluorescence imaging system

ABSTRACT

Fluorescence imaging with reduced fixed pattern noise is disclosed. A method includes actuating an emitter to emit a plurality of pulses of electromagnetic radiation and sensing reflected electromagnetic radiation resulting from the plurality of pulses of electromagnetic radiation with a pixel array of an image sensor to generate a plurality of exposure frames. The method includes applying edge enhancement to edges within an exposure frame of the plurality of exposure frames. The method is such that at least a portion of the plurality of pulses of electromagnetic radiation emitted by the emitter comprises one or more of electromagnetic radiation having a wavelength from about 770 nm to about 790 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/864,219, filed Jun. 20, 2015, titled “NOISE AWAREEDGE ENHANCEMENT IN A PULSED HYPERSPECTRAL AND FLUORESCENCE IMAGINGENVIRONMENT,” which is incorporated herein by reference in its entirety,including but not limited to those portions that specifically appearhereinafter, the incorporation by reference being made with thefollowing exception: In the event that any portion of theabove-referenced provisional application is inconsistent with thisapplication, this application supersedes the above-referencedprovisional application.

TECHNICAL FIELD

This disclosure is directed to digital imaging and is particularlydirected to fluorescence imaging in a light deficient environment.

BACKGROUND

Advances in technology have provided advances in imaging capabilitiesfor medical use. An endoscope may be used to look inside a body andexamine the interior of an organ or cavity of the body. Endoscopes areused for investigating a patient's symptoms, confirming a diagnosis, orproviding medical treatment. A medical endoscope may be used for viewinga variety of body systems and parts such as the gastrointestinal tract,the respiratory tract, the urinary tract, the abdominal cavity, and soforth. Endoscopes may further be used for surgical procedures such asplastic surgery procedures, procedures performed on joints or bones,procedures performed on the neurological system, procedures performedwithin the abdominal cavity, and so forth.

In some instances of endoscopic imaging, it may be beneficial ornecessary to view a space in color. A digital color image includes atleast three layers, or “color channels,” that cumulatively form an imagewith a range of hues. Each of the color channels measures the intensityand chrominance of light for a spectral band. Commonly, a digital colorimage includes a color channel for red, green, and blue spectral bandsof light (this may be referred to as a Red Green Blue or RGB image).Each of the red, green, and blue color channels include brightnessinformation for the red, green, or blue spectral band of light. Thebrightness information for the separate red, green, and blue layers arecombined to create the color image. Because a color image is made up ofseparate layers, a conventional digital camera image sensor includes acolor filter array that permits red, green, and blue visible lightwavelengths to hit selected pixel sensors. Each individual pixel sensorelement is made sensitive to red, green, or blue wavelengths and willonly return image data for that wavelength. The image data from thetotal array of pixel sensors is combined to generate the RGB image. Theat least three distinct types of pixel sensors consume significantphysical space such that the complete pixel array cannot fit in thesmall distal end of an endoscope.

Because a traditional image sensor cannot fit in the distal end of anendoscope, the image sensor is traditionally located in a handpiece unitof an endoscope that is held by an endoscope operator and is not placedwithin the body cavity. In such an endoscope, light is transmitted alongthe length of the endoscope from the handpiece unit to the distal end ofthe endoscope. This configuration has significant limitations.Endoscopes with this configuration are delicate and can be easilymisaligned or damaged when bumped or impacted during regular use. Thiscan significantly degrade the quality of the images and necessitate thatthe endoscope be frequently repaired or replaced.

The traditional endoscope with the image sensor placed in the handpieceunit is further limited to capturing only color images. However, in someimplementations, it may be desirable to capture images with fluorescenceimage data in addition to color image data. Fluorescence is the emissionof light by a substance that has absorbed light or other electromagneticradiation. Certain fluorescent materials “glow” or emit a distinct colorthat is visible to the human eye when the fluorescent material issubjected to ultraviolet light or other wavelengths of electromagneticradiation. Certain fluorescent materials will cease to glow nearlyimmediately when the radiation source stops.

Fluorescence occurs when an orbital electron of a molecule, atom, ornanostructure is excited by light or other electromagnetic radiation,and then relaxes to its ground state by emitting a photon from theexcited state. The specific frequencies of electromagnetic radiationthat excite the orbital electron, or are emitted by the photon duringrelaxation, are dependent on the atom, molecule, or nanostructure.Fluorescence imaging has numerous practical applications, includingmineralogy, gemology, medicine, spectroscopy for chemical sensors,detecting biological processes or signals, and others. Fluorescence canbe used in biochemistry and medicine as a non-destructive means fortracking or analyzing biological molecules. Some fluorescent reagents ordyes can be configured to attach to certain types of tissue and therebydraw attention to that type of tissue.

However, fluorescence imaging requires specialized emissions ofelectromagnetic radiation and specialized imaging sensors capable ofreading the specific relaxation wavelength for a specific fluorescentreagent. Different reagents or dyes are sensitive to differentwavelengths of electromagnetic radiation and emit different wavelengthsof electromagnetic radiation when fluoresced. A fluorescent imagingsystem may be highly specialized and tuned for a certain reagent or dye.Such imaging systems are useful for limited applications and are notcapable of fluorescing more than one reagent or structure during asingle imaging session. It is very costly to use multiple distinctimaging systems that are each configured for fluorescing a differentreagent. Additionally, it may be desirable to administer multiplefluorescent reagents in a single imaging session and view the multiplereagents in a single overlaid image.

In light of the foregoing, described herein are systems, methods, anddevices for fluorescent imaging in a light deficient environment. Suchsystems, methods, and devices may provide multiple datasets foridentifying critical structures in a body and providing precise andvaluable information about the body cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive implementations of the disclosure aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified. Advantages of the disclosure will becomebetter understood with regard to the following description andaccompanying drawings where:

FIG. 1 is a schematic view of a system for digital imaging in a lightdeficient environment with a paired emitter and pixel array;

FIG. 2 is a system for providing illumination to a light deficientenvironment for endoscopic imaging;

FIG. 2A is a schematic diagram of complementary system hardware;

FIGS. 3A to 3D are illustrations of the operational cycles of a sensorused to construct an exposure frame;

FIG. 4A is a graphical representation of the operation of an embodimentof an electromagnetic emitter;

FIG. 4B is a graphical representation of varying the duration andmagnitude of the emitted electromagnetic pulse to provide exposurecontrol;

FIG. 5 is a graphical representation of an embodiment of the disclosurecombining the operational cycles of a sensor, the electromagneticemitter, and the emitted electromagnetic pulses of FIGS. 3A-4B, whichdemonstrate the imaging system during operation;

FIG. 6A is a schematic diagram of a process for recording a video withfull spectrum light over a period of time from t(0) to t(1);

FIG. 6B is a schematic diagram of a process for recording a video bypulsing portioned spectrum light over a period of time from t(0) tot(1);

FIGS. 7A-7E illustrate schematic views of the processes over an intervalof time for recording a frame of video for both full spectrum light andpartitioned spectrum light;

FIG. 8 is a schematic diagram of a process flow to be implemented by acontroller or image signal processor for generating a video stream withRGB image frames and fluorescence imaging data overlaid on the RGB imageframe;

FIG. 9 is a schematic diagram of a process flow for applying superresolution and color motion artifact correction processes to image datathat may include luminance, chrominance, and hyperspectral data forgenerating a YCbCr or RGB image with fluorescence imaging data overlaidthereon;

FIG. 10 is a graphical representation of the shape of luminance y_(i) ofpixel, and the shape of the filtered version f_(i) of the luminance, andthe shape of the difference plane d_(i);

FIG. 11 is a graphical representation of how α might be construed todepend upon the modulus of d_(i);

FIG. 12 is a schematic flow chart diagram of a method for implementingedge enhancement processes on an image frame;

FIG. 13 is a schematic diagram of a pattern reconstruction process forgenerating an RGB image with fluorescence imaging data overlaid thereonby pulsing partitioned spectrums of light;

FIGS. 14A-14C illustrate a light source having a plurality of emitters;

FIG. 15 illustrates a single optical fiber outputting via a diffuser atan output to illuminate a scene in a light deficient environment;

FIG. 16 illustrates a portion of the electromagnetic spectrum dividedinto a plurality of different sub-spectrums which may be emitted byemitters of a light source in accordance with the principles andteachings of the disclosure;

FIG. 17 is a schematic diagram illustrating a timing sequence foremission and readout for generating an image frame comprising aplurality of exposure frames resulting from differing partitions ofpulsed light;

FIG. 18 illustrates an imaging system including a single cut filter forfiltering wavelengths of electromagnetic radiation;

FIG. 19 illustrates an imaging system comprising a multiple cut filterfor filtering wavelengths of electromagnetic radiation;

FIGS. 20A and 20B illustrate a perspective view and a side view,respectively, of an implementation of an imaging sensor having aplurality of pixel arrays for producing a three-dimensional image,wherein the plurality of pixel arrays and the image sensor are built ona plurality of substrates;

FIGS. 21A and 21B illustrate an implementation having a plurality ofpixel arrays for producing a three-dimensional image in accordance withthe principles and teachings of the disclosure; and

FIGS. 22A and 22B illustrate a perspective view and a side view,respectively, of an implementation of an imaging sensor built on aplurality of substrates, wherein a plurality of pixel columns formingthe pixel array are located on the first substrate and a plurality ofcircuit columns are located on a second substrate and showing anelectrical connection and communication between one column of pixels toits associated or corresponding column of circuitry.

DETAILED DESCRIPTION

Disclosed herein are systems, methods, and devices for digital imagingthat may be primarily suited to medical applications such as medicalendoscopic imaging. An embodiment of the disclosure is an endoscopicsystem for fluorescence and/or color imaging in a light deficientenvironment.

Conventional endoscopes are designed such that the image sensor isplaced at a proximal end of the device within a handpiece unit. Thisconfiguration requires that incident light travel the length of theendoscope by way of precisely coupled optical elements. The preciseoptical elements can easily be misaligned during regular use, and thiscan lead to image distortion or image loss. Embodiments of thedisclosure place an image sensor within a distal end of the endoscopeitself. This provides greater optical simplicity when compared withimplementations known in the art. However, an acceptable solution tothis approach is by no means trivial and introduces its own set ofengineering challenges, not least of which that the image sensor mustfit within a highly constrained area.

The imaging systems disclosed herein place aggressive constraints on thesize of the image sensor. This enables the image sensor to be placed ina distal end of an endoscope and thereby enables the correspondingbenefits of improved optical simplicity and increased mechanicalrobustness for the endoscope. However, placing these aggressiveconstraints on the image sensor area results in fewer and/or smallerpixels and can degrade image quality. An embodiment of the disclosureovercomes this challenge by incorporating a monochrome image sensor withminimal peripheral circuitry, connection pads, and logic. The imagingsystems disclosed herein provide means for extending the dynamic range,sensor sensitivity, and spatial resolution of resultant images whilestill decreasing the overall size of the image sensor through noiseaware edge enhancement.

For digital imaging systems, the final quality of a digital imagedepends on the engineering details of the electronic capture processthat was used to generate the image. The perceived quality of an imageis dependent on the signal to noise ratio (SNR), dynamic range (DR),spatial resolution, perception of visible unnatural artifacts,perception of spatial distortion, and color fidelity of the image. Eachof these factors can be negatively impacted by decreasing the overallsize of the image sensor. Therefore, in an effort to increase theperceived quality of a resultant image frame, traditional cameras knownin the art include multiple image sensors or include an enlarged imagesensor. For example, high-end cameras that can produce high resolutionimages typically include at least three monochrome sensors that areprecisely coupled in an elaborate arrangement of prisms and filters.Another traditional solution is to use a single sensor with individualpixel-sized color filters fabricated on to the image sensor in a mosaicarrangement. The most popular mosaic arrangement is the Bayer pattern.An image sensor with a Bayer pattern can be inexpensive to fabricate butcannot achieve the image quality realized by the three-image sensorsolution implemented in high-end cameras. An additional undesirable sideeffect of the Bayer pattern is that the color segmentation patternintroduces artifacts in the resultant image frames, and these artifactscan be especially noticeable around black and white edges.

One traditional approach to decreasing the size of the image sensor isto increase the number of pixels in the pixel array and reduce the sizeof the individual pixels. However, smaller pixels naturally have lowersignal capacity. The lower signal capacity reduces the dynamic range ofdata captured by the pixels and reduces the maximum possible signal tonoise ratio. Decreasing the area of an individual pixel reduces thesensitivity of the pixel not only in proportion with the capture area ofthe pixel but to a greater degree. The loss of sensitivity for the pixelmay be compensated by widening the aperture, but this leads to ashallower depth of field and shallower depth of focus. The shallowerdepth of field impacts the resolution of the resultant image and canlead to greater spatial distortion. Additionally, smaller pixels aremore challenging to manufacture consistently, and this may result ingreater defect rates.

In light of the deficiencies associated with decreasing the capture areaof the pixels, disclosed herein are systems, methods, and devices forreducing pixel count and bolstering image resolution by other means. Inan embodiment, a monochrome image sensor is used with “color agnostic”pixels in the pixel array. The color information is determined bycapturing independent exposure frames in response to pulses of differentwavelengths of electromagnetic radiation. The alternative pulses mayinclude red, green, and blue wavelengths for generating an RGB imageframe consisting of a red exposure frame, a green exposure frame, and ablue exposure frame. The image frame may further include data from afluorescence exposure frame overlaid on the RGB image frame. Thefluorescence excitation pulse may include one or more pulses ofelectromagnetic radiation for fluorescing a reagent or dye. In anembodiment, the fluorescence excitation emission includes one or more ofelectromagnetic radiation having a wavelength from about 770 nm to about790 nm and/or from about 795 nm to about 815 nm. Alternating thewavelengths of the pulsed electromagnetic radiation allows the fullpixel array to be exploited and avoids the artifacts introduced by Bayerpattern pixel arrays.

In an embodiment, each pulse or grouping of pulses of electromagneticradiation results in an exposure frame sensed by the pixel array. Aplurality of exposure frames may be combined to generate an image frame.The image frame may include, for example, a red exposure frame generatedin response to a red pulse, a green exposure frame generated in responseto a green pulse, a blue exposure frame generated in response to a bluepulse, and a fluorescence exposure frame generated in response to afluorescence excitation pulse. The red, green, blue, and fluorescenceexposure frames can be combined to generate a single RGB image framewith fluorescence data overlaid thereon. This method results inincreased dynamic range and spatial resolution in the resultant imageframe. However, this method can introduce motion blur because themultiple exposure frames making up the image frame are captured overtime. Additionally, because the independent exposure frames supplydifferent color components, the image frame can have unnatural coloredeffects that may be particularly visible in the vicinity of large edges.In light of the foregoing, the systems, methods, and devices disclosedherein correct for motion introduced by frame-wise color switching.

In an embodiment, a method is executed on an image to improve theperceived quality of the image. The method is deployed to perform noiseaware edge enhancement on the image that separates true edge and textureinformation from random noise. The method includes extracting luminancedata from the image and detecting edges of the image. The edges of theimage may be detected by deploying the Canny approach, the unsharp maskmethod, or some other suitable means. The method includes applying again factor to the edges of the image and merging the extractedluminance data with the edge data that has been modified by the appliedgain factor. The method may be deployed to generated improved RGB colorimages with increased perceived resolution.

In some instances, it is desirable to generate endoscopic imaging withmultiple data types or multiple images overlaid on one another. Forexample, it may be desirable to generate a color (Red Green Blue “RGB”)image that further includes fluorescence imaging data overlaid on theRGB image. An overlaid image of this nature may enable a medicalpractitioner or computer program to identify critical body structuresbased on the fluorescence imaging data. Historically, this would requirethe use of multiple sensor systems including an image sensor for colorimaging and one or more additional image sensors for fluorescenceimaging. In such systems, the multiple image sensors would have multipletypes of pixel sensors that are each sensitive to distinct ranges ofelectromagnetic radiation. In systems known in the art, this includesthe three separate types of pixel sensors for generating an RGB colorimage along with additional pixel sensors for generating thefluorescence image data at different wavelengths of the electromagneticspectrum. These multiple different pixel sensors consume a prohibitivelylarge physical space and cannot be located at a distal tip of theendoscope. In systems known in the art, the camera or cameras are notplaced at the distal tip of the endoscope and are instead placed in anendoscope handpiece or robotic unit. This introduces numerousdisadvantages and causes the endoscope to be very delicate. The delicateendoscope may be damaged and image quality may be degraded when theendoscope is bumped or impacted during use. Considering the foregoing,disclosed herein are systems, methods, and devices for endoscopicimaging in a light deficient environment. The systems, methods, anddevices disclosed herein provide means for employing multiple imagingtechniques in a single imaging session while permitting one or moreimage sensors to be disposed in a distal tip of the endoscope.

Fluorescence Imaging

The systems, methods, and devices disclosed herein provide means forgenerating fluorescence imaging data in a light deficient environment.The fluorescence imaging data may be used to identify certain materials,tissues, components, or processes within a body cavity or other lightdeficient environment. In certain embodiments, fluorescence imaging isprovided to a medical practitioner or computer-implemented program toenable the identification of certain structures or tissues within abody. Such fluorescence imaging data may be overlaid on black-and-whiteor RGB images to provide additional information and context.

Fluorescence is the emission of light by a substance that has absorbedlight or other electromagnetic radiation. Certain fluorescent materialsmay “glow” or emit a distinct color that is visible to the human eyewhen the fluorescent material is subjected to ultraviolet light or otherwavelengths of electromagnetic radiation. Certain fluorescent materialswill cease to glow nearly immediately when the radiation source stops.

Fluorescence occurs when an orbital electron of a molecule, atom, ornanostructure is excited by light or other electromagnetic radiation,and then relaxes to its ground state by emitting a photon from theexcited state. The specific frequencies of electromagnetic radiationthat excite the orbital electron, or are emitted by the photon duringrelaxation, are dependent on the particular atom, molecule, ornanostructure. In most cases, the light emitted by the substance has alonger wavelength, and therefore lower energy, than the radiation thatwas absorbed by the substance. However, when the absorbedelectromagnetic radiation is intense, it is possible for one electron toabsorb two photons. This two-photon absorption can lead to emission ofradiation having a shorter wavelength, and therefore higher energy, thanthe absorbed radiation. Additionally, the emitted radiation may also bethe same wavelength as the absorbed radiation.

Fluorescence imaging has numerous practical applications, includingmineralogy, gemology, medicine, spectroscopy for chemical sensors,detecting biological processes or signals, and so forth. Fluorescencemay particularly be used in biochemistry and medicine as anon-destructive means for tracking or analyzing biological molecules.The biological molecules, including certain tissues or structures, maybe tracked by analyzing the fluorescent emission of the biologicalmolecules after being excited by a certain wavelength of electromagneticradiation. However, relatively few cellular components are naturallyfluorescent. In certain implementations, it may be desirable tovisualize a certain tissue, structure, chemical process, or biologicalprocess that is not intrinsically fluorescent. In such animplementation, the body may be administered a dye or reagent that mayinclude a molecule, protein, or quantum dot having fluorescentproperties. The reagent or dye may then fluoresce after being excited bya certain wavelength of electromagnetic radiation. Different reagents ordyes may include different molecules, proteins, and/or quantum dots thatwill fluoresce at particular wavelengths of electromagnetic radiation.Thus, it may be necessary to excite the reagent or dye with aspecialized band of electromagnetic radiation to achieve fluorescenceand identify the desired tissue, structure, or process in the body.

Fluorescence imaging may provide valuable information in the medicalfield that may be used for diagnostic purposes and/or may be visualizedin real-time during a medical procedure. Specialized reagents or dyesmay be administered to a body to fluoresce certain tissues, structures,chemical processes, or biological processes. The fluorescence of thereagent or dye may highlight body structures such as blood vessels,nerves, particular organs, and so forth. Additionally, the fluorescenceof the reagent or dye may highlight conditions or diseases such ascancerous cells or cells experiencing a certain biological or chemicalprocess that may be associated with a condition or disease. Thefluorescence imaging may be used in real-time by a medical practitioneror computer program for differentiating between, for example, cancerousand non-cancerous cells during a surgical tumor extraction. Thefluorescence imaging may further be used as a non-destructive means fortracking and visualizing over time a condition in the body that wouldotherwise not be visible by the human eye or distinguishable in an RGBimage.

The systems, methods, and devices for generating fluorescence imagingdata may be used in coordination with reagents or dyes. Some reagents ordyes are known to attach to certain types of tissues and fluoresce atspecific wavelengths of the electromagnetic spectrum. In animplementation, a reagent or dye is administered to a patient that isconfigured to fluoresce when activated by certain wavelengths of light.The endoscopic imaging system disclosed herein is used to excite andfluoresce the reagent or dye. The fluorescence of the reagent or dye iscaptured by the endoscopic imaging system to aid in the identificationof tissues or structures in the body cavity. In an implementation, apatient is administered a plurality of reagents or dyes that are eachconfigured to fluoresce at different wavelengths and/or provide anindication of different structures, tissues, chemical reactions,biological processes, and so forth. In such an implementation, theendoscopic imaging system emits each of the applicable wavelengths tofluoresce each of the applicable reagents or dyes. This may negate theneed to perform individual imaging procedures for each of the pluralityof reagents or dyes.

Imaging reagents can enhance imaging capabilities in pharmaceutical,medical, biotechnology, diagnostic, and medical procedure industries.Many imaging techniques such as X-ray, computer tomography (CT),ultrasound, magnetic resonance imaging (MRI), and nuclear medicine,mainly analyze anatomy and morphology and are unable to detect changesat the molecular level. Fluorescent reagents, dyes, and probes,including quantum dot nanoparticles and fluorescent proteins, assistmedical imaging technologies by providing additional information aboutcertain tissues, structures, chemical processes, and/or biologicalprocesses that are present within the imaging region. Imaging usingfluorescent reagents enables cell tracking and/or the tracking ofcertain molecular biomarkers. Fluorescent reagents may be applied forimaging cancer, infection, inflammation, stem cell biology, and others.Numerous fluorescent reagents and dyes are being developed and appliedfor visualizing and tracking biological processes in a non-destructivemanner. Such fluorescent reagents may be excited by a certain wavelengthor band of wavelengths of electromagnetic radiation. Similarly, thosefluorescent reagents may emit relaxation energy at a certain wavelengthor band of wavelengths when fluorescing, and the emitted relaxationenergy may be read by a sensor to determine the location and/orboundaries of the reagent or dye.

In an embodiment of the disclosure, an endoscopic imaging system pulseselectromagnetic radiation for exciting an electron in a fluorescentreagent or dye. The endoscopic imaging system may pulse multipledifferent wavelengths of electromagnetic radiation for fluorescingmultiple different reagents or dyes during a single imaging session. Theendoscope includes an image sensor that is sensitive to the relaxationwavelength(s) of the one or more reagents or dyes. The imaging datagenerated by the image sensor can be used to identify a location andboundary of the one or more reagents or dyes. The endoscope system mayfurther pulse electromagnetic radiation in red, green, and blue bands ofvisible light such that the fluorescence imaging can be overlaid on anRGB video stream.

Pulsed Imaging

Some implementations of the disclosure include aspects of a combinedsensor and system design that allows for high definition imaging withreduced pixel counts in a controlled illumination environment. This isaccomplished with frame-by-frame pulsing of a single-color wavelengthand switching or alternating each frame between a single, differentcolor wavelength using a controlled light source in conjunction withhigh frame capture rates and a specially designed correspondingmonochromatic sensor. Additionally, electromagnetic radiation outsidethe visible light spectrum may be pulsed to enable the generation of afluorescence image by emitting the fluorescence excitation wavelengthfor a fluorescent reagent or dye. The pixels may be color agnostic suchthat each pixel generates data for each pulse of electromagneticradiation, including pulses for red, green, and blue visible lightwavelengths along with other wavelengths used for fluorescence imaging.

For the purposes of promoting an understanding of the principles inaccordance with the disclosure, reference will now be made to theembodiments illustrated in the drawings and specific language will beused to describe the same. It will nevertheless be understood that nolimitation of the scope of the disclosure is thereby intended. Anyalterations and further modifications of the inventive featuresillustrated herein, and any additional applications of the principles ofthe disclosure as illustrated herein, which would normally occur to oneskilled in the relevant art and having possession of this disclosure,are to be considered within the scope of the disclosure claimed.

Before the structure, systems and methods for producing an image in alight deficient environment are disclosed and described, it is to beunderstood that this disclosure is not limited to the particularstructures, configurations, process steps, and materials disclosedherein as such structures, configurations, process steps, and materialsmay vary somewhat. It is also to be understood that the terminologyemployed herein is used for the purpose of describing particularembodiments only and is not intended to be limiting since the scope ofthe disclosure will be limited only by the appended claims andequivalents thereof.

In describing and claiming the subject matter of the disclosure, thefollowing terminology will be used in accordance with the definitionsset out below.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise.

As used herein, the terms “comprising,” “including,” “containing,”“characterized by,” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, unrecited elements ormethod steps.

As used herein, the phrase “consisting of” and grammatical equivalentsthereof exclude any element or step not specified in the claim.

As used herein, the phrase “consisting essentially of” and grammaticalequivalents thereof limit the scope of a claim to the specifiedmaterials or steps and those that do not materially affect the basic andnovel characteristic or characteristics of the claimed disclosure.

As used herein, the term “proximal” shall refer broadly to the conceptof a portion nearest an origin.

As used herein, the term “distal” shall generally refer to the oppositeof proximal, and thus to the concept of a portion farther from anorigin, or a furthest portion, depending upon the context.

As used herein, color sensors or multi spectrum sensors are thosesensors known to have a color filter array (CFA) thereon to filter theincoming electromagnetic radiation into its separate components. In thevisual range of the electromagnetic spectrum, such a CFA may be built ona Bayer pattern or modification thereon to separate green, red and bluespectrum components of the light.

As used herein, monochromatic sensor refers to an unfiltered imagingsensor. Since the pixels are color agnostic, the effective spatialresolution is appreciably higher than for their color (typicallyBayer-pattern filtered) counterparts in conventional single-sensorcameras. Monochromatic sensors may also have higher quantum efficiencybecause fewer incident photons are wasted between individual pixels.

As used herein, an emitter is a device that is capable of generating andemitting electromagnetic pulses. Various embodiments of emitters may beconfigured to emit pulses and have very specific frequencies or rangesof frequencies from within the entire electromagnetic spectrum. Pulsesmay comprise wavelengths from the visible and non-visible ranges. Anemitter may be cycled on and off to produce a pulse or may produce apulse with a shutter mechanism. An emitter may have variable poweroutput levels or may be controlled with a secondary device such as anaperture or filter. An emitter may emit broad spectrum or full spectrumelectromagnetic radiation that may produce pulses through colorfiltering or shuttering. An emitter may comprise a plurality ofelectromagnetic sources that act individually or in concert.

It should be noted that as used herein the term “light” is both aparticle and a wavelength and is intended to denote electromagneticradiation that is detectable by a pixel array 122 and may includewavelengths from the visible and non-visible spectrums ofelectromagnetic radiation. The term “partition” is used herein to mean apre-determined range of wavelengths of the electromagnetic spectrum thatis less than the entire spectrum, or in other words, wavelengths thatmake up some portion of the electromagnetic spectrum. As used herein, anemitter is a light source that may be controllable as to the portion ofthe electromagnetic spectrum that is emitted or that may operate as tothe physics of its components, the intensity of the emissions, or theduration of the emission, or all the above. An emitter may emit light inany dithered, diffused, or collimated emission and may be controlleddigitally or through analog methods or systems. As used herein, anelectromagnetic emitter is a source of a burst of electromagnetic energyand includes light sources, such as lasers, LEDs, incandescent light, orany light source that can be digitally controlled.

Referring now to the figures, FIG. 1 illustrates a schematic diagram ofa system 100 for sequential pulsed imaging in a light deficientenvironment. The system 100 can be deployed to generate an RGB imagewith fluorescence imaging data overlaid on the RGB image. The system 100includes an emitter 102 and a pixel array 122. The emitter 102 pulses apartition of electromagnetic radiation in the light deficientenvironment 112 and the pixel array 122 senses instances of reflectedelectromagnetic radiation. The emitter 102 and the pixel array 122 workin sequence such that one or more pulses of a partition ofelectromagnetic radiation results in image data sensed by the pixelarray 122.

It should be noted that as used herein the term “light” is both aparticle and a wavelength and is intended to denote electromagneticradiation that is detectable by a pixel array 122 and may includewavelengths from the visible and non-visible spectrums ofelectromagnetic radiation. The term “partition” is used herein to mean apre-determined range of wavelengths of the electromagnetic spectrum thatis less than the entire spectrum, or in other words, wavelengths thatmake up some portion of the electromagnetic spectrum. As used herein, anemitter is a light source that may be controllable as to the portion ofthe electromagnetic spectrum that is emitted or that may operate as tothe physics of its components, the intensity of the emissions, or theduration of the emission, or all the above. An emitter may emit light inany dithered, diffused, or collimated emission and may be controlleddigitally or through analog methods or systems. As used herein, anelectromagnetic emitter is a source of a burst of electromagnetic energyand includes light sources, such as lasers, LEDs, incandescent light, orany light source that can be digitally controlled.

A pixel array 122 of an image sensor may be paired with the emitter 102electronically, such that the emitter 102 and the pixel array 122 aresynced during operation for both receiving the emissions and for theadjustments made within the system. The emitter 102 may be tuned to emitelectromagnetic radiation in the form of a laser, which may be pulsed toilluminate a light deficient environment 112. The emitter 102 may pulseat an interval that corresponds to the operation and functionality ofthe pixel array 122. The emitter 102 may pulse light in a plurality ofelectromagnetic partitions such that the pixel array receiveselectromagnetic energy and produces a dataset that corresponds in timewith each specific electromagnetic partition. For example, FIG. 1illustrates an implementation wherein the emitter 102 emits fourdifferent partitions of electromagnetic radiation, including red 104,green 106, blue 108, and a fluorescence excitation 110 wavelength. Thefluorescence excitation 110 wavelength may include a plurality ofdifferent partitions of electromagnetic radiation that are selected tofluoresce a plurality of fluorescent reagents that are present withinthe light deficient environment 112. The fluorescent excitation 110wavelength may be selected to fluoresce a particular fluorescent reagentthat is present in the light deficient environment 112.

The light deficient environment 112 includes structures, tissues, andother elements that reflect a combination of red 114, green 116, and/orblue 118 light. A structure that is perceived as being red 114 willreflect back pulsed red 104 light. The reflection off the red structureresults in sensed red 105 by the pixel array 122 following the pulsedred 104 emission. The data sensed by the pixel array 122 results in ared exposure frame. A structure that is perceived as being green 116will reflect back pulsed green 106 light. The reflection off the greenstructure results in sensed green 107 by the pixel array 122 followingthe pulsed green 106 emission. The data sensed by the pixel array 122results in a green exposure frame. A structure that is perceived asbeing blue 118 will reflect back pulsed blue 108 light. The reflectionoff the blue structure results in sensed blue 109 by the pixel array 122following the pulsed blue 108 emission. The data sensed by the pixelarray 122 results in a blue exposure frame.

When a structure is a combination of colors, the structure will reflectback a combination of the pulsed red 104, pulsed green 106, and/orpulsed blue 108 emissions. For example, a structure that is perceived asbeing purple will reflect back light from the pulsed red 104 and pulsedblue 108 emissions. The resulting data sensed by the pixel array 122will indicate that light was reflected in the same region following thepulsed red 104 and pulsed blue 108 emissions. When the resultant redexposure frame and blue exposure frames are combined to form the RGBimage frame, the RGB image frame will indicate that the structure ispurple.

In an embodiment where the light deficient environment 112 includes afluorescent reagent or dye or includes one or more fluorescentstructures, tissues, or other elements, the pulsing scheme may includethe emission of a certain fluorescence excitation wavelength. Thecertain fluorescence excitation wavelength may be selected to fluorescea known fluorescent reagent, dye, or other structure. The fluorescentstructure will be sensitive to the fluorescence excitation wavelengthand will emit a fluorescence relaxation wavelength. The fluorescencerelaxation wavelength will be sensed by the pixel array 122 followingthe emission of the fluorescence excitation wavelength. The data sensedby the pixel array 122 results in a fluorescence exposure frame. Thefluorescence exposure frame may be combined with multiple other exposureframes to form an image frame. The data in the fluorescence exposureframe may be overlaid on an RGB image frame that includes data from ared exposure frame, a green exposure frame, and a blue exposure frame.

In an embodiment where the light deficient environment 112 includesstructures, tissues, or other materials that emit a spectral response tocertain partitions of the electromagnetic spectrum, the pulsing schememay include the emission of a hyperspectral partition of electromagneticradiation for the purpose of eliciting the spectral response from thestructures, tissues, or other materials present in the light deficientenvironment 112. The spectral response includes the emission orreflection of certain wavelengths of electromagnetic radiation. Thespectral response can be sensed by the pixel array 122 and result in ahyperspectral exposure frame. The hyperspectral exposure frame may becombined with multiple other exposure frames to form an image frame. Thedata in the hyperspectral exposure frame may be overlaid on an RGB imageframe that includes data from a red exposure frame, a green exposureframe, and a blue exposure frame.

In an embodiment, the pulsing scheme includes the emission of a lasermapping or tool tracking pattern. The reflected electromagneticradiation sensed by the pixel array 122 following the emission of thelaser mapping or tool tracking pattern results in a laser mappingexposure frame. The data in the laser mapping exposure frame may beprovided to a corresponding system to identify, for example, distancesbetween tools present in the light deficient environment 112, athree-dimensional surface topology of a scene in the light deficientenvironment 112, distances, dimensions, or positions of structures orobjects within the scene, and so forth. This data may be overlaid on anRGB image frame or otherwise provided to a user of the system.

The emitter 102 may be a laser emitter that is capable of emittingpulsed red 104 light for generating sensed red 105 data for identifyingred 114 elements within the light deficient environment 112. The emitter102 is further capable of emitting pulsed green 106 light for generatingsensed green 107 data for identifying green 116 elements within thelight deficient environment. The emitter 102 is further capable ofemitting pulsed blue 108 light for generating sensed blue 109 data foridentifying blue 118 elements within the light deficient environment.The emitter 102 is further capable of emitting pulsed fluorescenceexcitation 110 wavelength(s) of electromagnetic radiation foridentifying a fluorescent reagent 120 within the light deficientenvironment 112. The fluorescent reagent 120 is identified by excitingthe fluorescent reagent 120 with the pulsed fluorescence excitation 110light and then sensing (by the pixel array 122) the fluorescencerelaxation 111 wavelength for that particular fluorescent reagent 120.The emitter 102 is capable of emitting the pulsed red 104, pulsed green106, pulsed blue 108, and pulsed fluorescence excitation 110 wavelengthsin any desired sequence.

The pixel array 122 senses reflected electromagnetic radiation. Each ofthe sensed red 105, the sensed green 107, the sensed blue 109, and thesensed fluorescence relaxation 111 data can be referred to as an“exposure frame.” Each exposure frame is assigned a specific color orwavelength partition, wherein the assignment is based on the timing ofthe pulsed color or wavelength partition from the emitter 102. Theexposure frame in combination with the assigned specific color orwavelength partition may be referred to as a dataset. Even though thepixels 122 are not color-dedicated, they can be assigned a color for anygiven dataset based on a priori information about the emitter.

For example, during operation, after pulsed red 104 light is pulsed inthe light deficient environment 112, the pixel array 122 sensesreflected electromagnetic radiation. The reflected electromagneticradiation results in an exposure frame, and the exposure frame iscatalogued as sensed red 105 data because it corresponds in time withthe pulsed red 104 light. The exposure frame in combination with anindication that it corresponds in time with the pulsed red 104 light isthe “dataset.” This is repeated for each partition of electromagneticradiation emitted by the emitter 102. The data created by the pixelarray 122 includes the sensed red 105 exposure frame identifying red 114components in the light deficient environment and corresponding in timewith the pulsed red 104 light. The data further includes the sensedgreen 107 exposure frame identifying green 116 components in the lightdeficient environment and corresponding in time with the pulsed green106 light. The data further includes the sensed blue 109 exposure frameidentifying blue 118 components in the light deficient environment andcorresponding in time with the pulsed blue 108 light. The data furtherincludes the sensed fluorescence relaxation 111 exposure frameidentifying the fluorescent reagent 120 and corresponding in time withthe pulsed fluorescence excitation 110 wavelength(s) of light.

In one embodiment, three datasets representing RED, GREEN and BLUEelectromagnetic pulses are combined to form a single image frame. Thus,the information in a red exposure frame, a green exposure frame, and ablue exposure frame are combined to form a single RGB image frame. Oneor more additional datasets representing other wavelength partitions maybe overlaid on the single RGB image frame. The one or more additionaldatasets may represent, for example, fluorescence imaging responsive tothe pulsed excitation 110 wavelength between 770 nm and 790 nm andbetween 795 nm and 815 nm.

It will be appreciated that the disclosure is not limited to anyparticular color combination or any particular electromagneticpartition, and that any color combination or any electromagneticpartition may be used in place of RED, GREEN and BLUE, such as Cyan,Magenta and Yellow; Ultraviolet; infrared; any combination of theforegoing, or any other color combination, including all visible andnon-visible wavelengths, without departing from the scope of thedisclosure. In the figure, the light deficient environment 112 to beimaged includes red 114, green 116, and blue 118 portions, and furtherincludes a fluorescent reagent 120. As illustrated in the figure, thereflected light from the electromagnetic pulses only contains the datafor the portion of the object having the specific color that correspondsto the pulsed color partition. Those separate color (or color interval)datasets can then be used to reconstruct the image by combining thedatasets at 126. The information in each of the multiple exposure frames(i.e., the multiple datasets) may be combined by a controller 124, acontrol unit, a camera control unit, the image sensor, an image signalprocessing pipeline, or some other computing resource that isconfigurable to process the multiple exposure frames and combine thedatasets at 126. The datasets may be combined to generate the singleimage frame within the endoscope unit itself or offsite by some otherprocessing resource.

FIG. 2 is a system 200 for providing illumination to a light deficientenvironment, such as for endoscopic imaging. The system 200 may be usedin combination with any of the systems, methods, or devices disclosedherein. The system 200 includes an emitter 202, a controller 204, ajumper waveguide 206, a waveguide connector 208, a lumen waveguide 210,a lumen 212, and an image sensor 214 with accompanying opticalcomponents (such as a lens). The emitter 202 (may be genericallyreferred to as a “light source”) generates light that travels throughthe jumper waveguide 206 and the lumen waveguide 210 to illuminate ascene at a distal end of the lumen 212. The emitter 202 may be used toemit any wavelength of electromagnetic energy including visiblewavelengths, infrared, ultraviolet, hyperspectral, fluorescenceexcitation, laser mapping pulsing schemes, or other wavelengths. Thelumen 212 may be inserted into a patient's body for imaging, such asduring a procedure or examination. The light is output as illustrated bydashed lines 216. A scene illuminated by the light may be captured usingthe image sensor 214 and displayed for a doctor or some other medicalpersonnel. The controller 204 may provide control signals to the emitter202 to control when illumination is provided to a scene. In oneembodiment, the emitter 202 and controller 204 are located within acamera control unit (CCU) or external console to which an endoscope isconnected. If the image sensor 214 includes a CMOS sensor, light may beperiodically provided to the scene in a series of illumination pulsesbetween readout periods of the image sensor 214 during what is known asa blanking period. Thus, the light may be pulsed in a controlled mannerto avoid overlapping into readout periods of the image pixels in a pixelarray of the image sensor 214.

In one embodiment, the lumen waveguide 210 includes one or more opticalfibers. The optical fibers may be made of a low-cost material, such asplastic to allow for disposal of the lumen waveguide 210 and/or otherportions of an endoscope. In one embodiment, the lumen waveguide 210 isa single glass fiber having a diameter of 500 microns. The jumperwaveguide 206 may be permanently attached to the emitter 202. Forexample, a jumper waveguide 206 may receive light from an emitter withinthe emitter 202 and provide that light to the lumen waveguide 210 at thelocation of the connector 208. In one embodiment, the jumper waveguide106 includes one or more glass fibers. The jumper waveguide may includeany other type of waveguide for guiding light to the lumen waveguide210. The connector 208 may selectively couple the jumper waveguide 206to the lumen waveguide 210 and allow light within the jumper waveguide206 to pass to the lumen waveguide 210. In one embodiment, the lumenwaveguide 210 is directly coupled to a light source without anyintervening jumper waveguide 206.

The image sensor 214 includes a pixel array. In an embodiment, the imagesensor 214 includes two or more pixel arrays for generating athree-dimensional image. The image sensor 214 may constitute two moreimage sensors that each have an independent pixel array and can operateindependent of one another. The pixel array of the image sensor 214includes active pixels and optical black (“OB”) or optically blindpixels. The active pixels may be clear “color agnostic” pixels that arecapable of sensing imaging data for any wavelength of electromagneticradiation. The optical black pixels are read during a blanking period ofthe pixel array when the pixel array is “reset” or calibrated. In anembodiment, light is pulsed during the blanking period of the pixelarray when the optical black pixels are being read. After the opticalblack pixels have been read, the active pixels are read during a readoutperiod of the pixel array. The active pixels may be charged by theelectromagnetic radiation that is pulsed during the blanking period suchthat the active pixels are ready to be read by the image sensor duringthe readout period of the pixel array.

FIG. 2A is a schematic diagram of complementary system hardware such asa special purpose or general-purpose computer. Implementations withinthe scope of the present disclosure may also include physical and othernon-transitory computer readable media for carrying or storing computerexecutable instructions and/or data structures. Such computer readablemedia can be any available media that can be accessed by a generalpurpose or special purpose computer system. Computer readable media thatstores computer executable instructions are computer storage media(devices). Computer readable media that carry computer executableinstructions are transmission media. Thus, by way of example, and notlimitation, implementations of the disclosure can comprise at least twodistinctly different kinds of computer readable media: computer storagemedia (devices) and transmission media.

Computer storage media (devices) includes RAM, ROM, EEPROM, CD-ROM,solid state drives (“SSDs”) (e.g., based on RAM), Flash memory,phase-change memory (“PCM”), other types of memory, other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium which can be used to store desired program code means inthe form of computer executable instructions or data structures andwhich can be accessed by a general purpose or special purpose computer.

A “network” is defined as one or more data links that enable thetransport of electronic data between computer systems and/or modulesand/or other electronic devices. In an implementation, a sensor andcamera control unit may be networked to communicate with each other, andother components, connected over the network to which they areconnected. When information is transferred or provided over a network oranother communications connection (either hardwired, wireless, or acombination of hardwired or wireless) to a computer, the computerproperly views the connection as a transmission medium. Transmissionsmedia can include a network and/or data links, which can be used tocarry desired program code means in the form of computer executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer. Combinations of the above shouldalso be included within the scope of computer readable media.

Further, upon reaching various computer system components, program codemeans in the form of computer executable instructions or data structuresthat can be transferred automatically from transmission media tocomputer storage media (devices) (or vice versa). For example, computerexecutable instructions or data structures received over a network ordata link can be buffered in RAM within a network interface module(e.g., a “NIC”), and then eventually transferred to computer system RAMand/or to less volatile computer storage media (devices) at a computersystem. RAM can also include solid state drives (SSDs or PCIx based realtime memory tiered storage, such as FusionIO). Thus, it should beunderstood that computer storage media (devices) can be included incomputer system components that also (or even primarily) utilizetransmission media.

Computer executable instructions comprise, for example, instructions anddata which, when executed by one or more processors, cause ageneral-purpose computer, special purpose computer, or special purposeprocessing device to perform a certain function or group of functions.The computer executable instructions may be, for example, binaries,intermediate format instructions such as assembly language, or evensource code. Although the subject matter has been described in languagespecific to structural features and/or methodological acts, it is to beunderstood that the subject matter defined in the appended claims is notnecessarily limited to the described features or acts described above.Rather, the described features and acts are disclosed as example formsof implementing the claims.

Those skilled in the art will appreciate that the disclosure may bepracticed in network computing environments with many types of computersystem configurations, including, personal computers, desktop computers,laptop computers, message processors, control units, camera controlunits, hand-held devices, hand pieces, multi-processor systems,microprocessor-based or programmable consumer electronics, network PCs,minicomputers, mainframe computers, mobile telephones, PDAs, tablets,pagers, routers, switches, various storage devices, and the like. Itshould be noted that any of the above-mentioned computing devices may beprovided by or located within a brick and mortar location. Thedisclosure may also be practiced in distributed system environmentswhere local and remote computer systems, which are linked (either byhardwired data links, wireless data links, or by a combination ofhardwired and wireless data links) through a network, both performtasks. In a distributed system environment, program modules may belocated in both local and remote memory storage devices.

Further, where appropriate, functions described herein can be performedin one or more of: hardware, software, firmware, digital components, oranalog components. For example, one or more application specificintegrated circuits (ASICs) or field programmable gate arrays (FPGAs)can be programmed to carry out one or more of the systems and proceduresdescribed herein. Certain terms are used throughout the followingdescription and Claims to refer to particular system components. As oneskilled in the art will appreciate, components may be referred to bydifferent names. This document does not intend to distinguish betweencomponents that differ in name, but not function.

FIG. 2A is a block diagram illustrating an example computing device 250.Computing device 250 may be used to perform various procedures, such asthose discussed herein. Computing device 250 can function as a server, aclient, or any other computing entity. Computing device 250 can performvarious monitoring functions as discussed herein, and can execute one ormore application programs, such as the application programs describedherein. Computing device 250 can be any of a wide variety of computingdevices, such as a desktop computer, a notebook computer, a servercomputer, a handheld computer, camera control unit, tablet computer andthe like.

Computing device 250 includes one or more processor(s) 252, one or morememory device(s) 254, one or more interface(s) 256, one or more massstorage device(s) 258, one or more Input/Output (I/O) device(s) 260, anda display device 280 all of which are coupled to a bus 262. Processor(s)252 include one or more processors or controllers that executeinstructions stored in memory device(s) 254 and/or mass storagedevice(s) 258. Processor(s) 252 may also include various types ofcomputer readable media, such as cache memory.

Memory device(s) 254 include various computer readable media, such asvolatile memory (e.g., random access memory (RAM) 264) and/ornonvolatile memory (e.g., read-only memory (ROM) 266). Memory device(s)254 may also include rewritable ROM, such as Flash memory.

Mass storage device(s) 258 include various computer readable media, suchas magnetic tapes, magnetic disks, optical disks, solid-state memory(e.g., Flash memory), and so forth. As shown in FIG. 2, a particularmass storage device is a hard disk drive 274. Various drives may also beincluded in mass storage device(s) 258 to enable reading from and/orwriting to the various computer readable media. Mass storage device(s)258 include removable media 276 and/or non-removable media.

I/O device(s) 260 include various devices that allow data and/or otherinformation to be input to or retrieved from computing device 250.Example I/O device(s) 260 include digital imaging devices,electromagnetic sensors and emitters, cursor control devices, keyboards,keypads, microphones, monitors or other display devices, speakers,printers, network interface cards, modems, lenses, CCDs or other imagecapture devices, and the like.

Display device 280 includes any type of device capable of displayinginformation to one or more users of computing device 250. Examples ofdisplay device 280 include a monitor, display terminal, video projectiondevice, and the like.

Interface(s) 256 include various interfaces that allow computing device250 to interact with other systems, devices, or computing environments.Example interface(s) 256 may include any number of different networkinterfaces 270, such as interfaces to local area networks (LANs), widearea networks (WANs), wireless networks, and the Internet. Otherinterface(s) include user interface 268 and peripheral device interface272. The interface(s) 256 may also include one or more user interfaceelements 268. The interface(s) 256 may also include one or moreperipheral interfaces such as interfaces for printers, pointing devices(mice, track pad, etc.), keyboards, and the like.

Bus 262 allows processor(s) 252, memory device(s) 254, interface(s) 256,mass storage device(s) 258, and I/O device(s) 260 to communicate withone another, as well as other devices or components coupled to bus 262.Bus 262 represents one or more of several types of bus structures, suchas a system bus, PCI bus, IEEE 1394 bus, USB bus, and so forth.

For purposes of illustration, programs and other executable programcomponents are shown herein as discrete blocks, although it isunderstood that such programs and components may reside at various timesin different storage components of computing device 250 and are executedby processor(s) 252. Alternatively, the systems and procedures describedherein can be implemented in hardware, or a combination of hardware,software, and/or firmware. For example, one or more application specificintegrated circuits (ASICs) or field programmable gate arrays (FPGAs)can be programmed to carry out one or more of the systems and proceduresdescribed herein.

FIG. 3A illustrates the operational cycles of a sensor used in rollingreadout mode or during the sensor readout 300. The frame readout periodmay start at and may be represented by vertical line 310. The readoutperiod 302 is represented by the diagonal or slanted line. The sensormay be read out on a row by row basis, the top of the downwards slantededge being the sensor top row 312 and the bottom of the downwardsslanted edge being the sensor bottom row 314. The time between the lastrow readout and the next readout period may be called the blankingperiod 316. It should be noted that some of the sensor pixel rows mightbe covered with a light shield (e.g., a metal coating or any othersubstantially black layer of another material type). These covered pixelrows may be referred to as optical black rows 318 and 320. Optical blackrows 318 and 320 may be used as input for correction algorithms. Asshown in FIG. 3A, these optical black rows 318 and 320 may be located onthe top of the pixel array or at the bottom of the pixel array or at thetop and the bottom of the pixel array.

FIG. 3B illustrates a process of controlling the amount ofelectromagnetic radiation, e.g., light, that is exposed to a pixel,thereby integrated or accumulated by the pixel. It will be appreciatedthat photons are elementary particles of electromagnetic radiation.Photons are integrated, absorbed, or accumulated by each pixel andconverted into an electrical charge or current. An electronic shutter orrolling shutter (shown by dashed line 322) may be used to start theintegration time by resetting the pixel. The light will then integrateuntil the next readout period. The position of the electronic shutter322 can be moved between two readout periods 302 to control the pixelsaturation for a given amount of light. It should be noted that thistechnique allows for a constant integration time between two differentlines but introduces a delay when moving from top to bottom rows.

FIG. 3C illustrates the case where the electronic shutter 322 has beenremoved. In this configuration, the integration of the incoming lightmay start during the readout period 302 and may end at the next readoutperiod 302, which also defines the start of the next integration.

FIG. 3D shows a configuration without an electronic shutter 322, butwith a controlled and pulsed light 330 during the blanking period 316.This ensures that all rows see the same light issued from the same lightpulse 330. In other words, each row will start its integration in a darkenvironment, which may be at the optical black back row 320 of read outframe (m) for a maximum light pulse width, and will then receive a lightstrobe and will end its integration in a dark environment, which may beat the optical black front row 318 of the next succeeding read out frame(m+1) for a maximum light pulse width. In the FIG. 3D example, the imagegenerated from the light pulse will be solely available during frame(m+1) readout without any interference with frames (m) and (m+2). Itshould be noted that the condition to have a light pulse to be read outonly in one frame and not interfere with neighboring frames is to havethe given light pulse firing during the blanking period 316. Because theoptical black rows 318, 320 are insensitive to light, the optical blackback rows 320 time of frame (m) and the optical black front rows 318time of frame (m+1) can be added to the blanking period 316 to determinethe maximum range of the firing time of the light pulse 330.

As illustrated in the FIG. 3A, a sensor may be cycled many times toreceive data for each pulsed color or wavelength (e.g., Red, Green,Blue, or other wavelength on the electromagnetic spectrum). Each cyclemay be timed. In an embodiment, the cycles may be timed to operatewithin an interval of 16.67 ms. In another embodiment, the cycles may betimed to operate within an interval of 8.3 ms. It will be appreciatedthat other timing intervals are contemplated by the disclosure and areintended to fall within the scope of this disclosure.

FIG. 4A graphically illustrates the operation of an embodiment of anelectromagnetic emitter. An emitter may be timed to correspond with thecycles of a sensor, such that electromagnetic radiation is emittedwithin the sensor operation cycle and/or during a portion of the sensoroperation cycle. FIG. 4A illustrates Pulse 1 at 402, Pulse 2 at 404, andPulse 3 at 406. In an embodiment, the emitter may pulse during thereadout period 302 of the sensor operation cycle. In an embodiment, theemitter may pulse during the blanking period 316 of the sensor operationcycle. In an embodiment, the emitter may pulse for a duration that isduring portions of two or more sensor operational cycles. In anembodiment, the emitter may begin a pulse during the blanking period316, or during the optical black portion 320 of the readout period 302,and end the pulse during the readout period 302, or during the opticalblack portion 318 of the readout period 302 of the next succeedingcycle. It will be understood that any combination of the above isintended to fall within the scope of this disclosure as long as thepulse of the emitter and the cycle of the sensor correspond.

FIG. 4B graphically represents varying the duration and magnitude of theemitted electromagnetic pulse (e.g., Pulse 1 at 412, Pulse 2 at 414, andPulse 3 at 416) to control exposure. An emitter having a fixed outputmagnitude may be pulsed during any of the cycles noted above in relationto FIGS. 3D and 4A for an interval to provide the needed electromagneticenergy to the pixel array. An emitter having a fixed output magnitudemay be pulsed at a longer interval of time, thereby providing moreelectromagnetic energy to the pixels or the emitter may be pulsed at ashorter interval of time, thereby providing less electromagnetic energy.Whether a longer or shorter interval time is needed depends upon theoperational conditions.

In contrast to adjusting the interval of time the emitter pulses a fixedoutput magnitude, the magnitude of the emission itself may be increasedto provide more electromagnetic energy to the pixels. Similarly,decreasing the magnitude of the pulse provides less electromagneticenergy to the pixels. It should be noted that an embodiment of thesystem may have the ability to adjust both magnitude and durationconcurrently, if desired. Additionally, the sensor may be adjusted toincrease its sensitivity and duration as desired for optimal imagequality. FIG. 4B illustrates varying the magnitude and duration of thepulses. In the illustration, Pulse 1 at 412 has a higher magnitude orintensity than either Pulse 2 at 414 or Pulse 3 at 416. Additionally,Pulse 1 at 412 has a shorter duration than Pulse 2 at 414 or Pulse 3 at416, such that the electromagnetic energy provided by the pulse isillustrated by the area under the pulse shown in the illustration. Inthe illustration, Pulse 2 at 414 has a relatively low magnitude orintensity and a longer duration when compared to either Pulse 1 at 412or Pulse 3 at 416. Finally, in the illustration, Pulse 3 at 416 has anintermediate magnitude or intensity and duration, when compared to Pulse1 at 412 and Pulse 2 at 414.

FIG. 5 is a graphical representation of an embodiment of the disclosurecombining the operational cycles, the electromagnetic emitter, and theemitted electromagnetic pulses of FIGS. 3A-3D and 4A to demonstrate theimaging system during operation in accordance with the principles andteachings of the disclosure. As can be seen in the figure, theelectromagnetic emitter pulses the emissions primarily during theblanking period 316 of the image sensor such that the pixels will becharged and ready to read during the readout period 302 of the imagesensor cycle. The dashed lines in FIG. 5 represent the pulses ofelectromagnetic radiation (from FIG. 4A). The pulses of electromagneticradiation are primarily emitted during the blanking period 316 of theimage sensor but may overlap with the readout period 302 of the imagesensor.

An exposure frame includes the data read by the pixel array of the imagesensor during a readout period 302. The exposure frame may be combinedwith an indication of what type of pulse was emitted by the emitterprior to the readout period 302. The combination of the exposure frameand the indication of the pulse type may be referred to as a dataset.Multiple exposure frames may be combined to generate a black-and-whiteor RGB color image. Additionally, hyperspectral, fluorescence, and/orlaser mapping imaging data may be overlaid on a black-and-white or RGBimage.

In an embodiment, an exposure frame is the data sensed by the pixelarray during the readout period 302 that occurs subsequent to a blankingperiod 316. The emission of electromagnetic radiation is emitted duringthe blanking period 316. In an embodiment, a portion of the emission ofelectromagnetic radiation overlaps the readout period 302. The blankingperiod 316 occurs when optical black pixels of the pixel array are beingread and the readout period 302 occurs when active pixels of the pixelarray are being read. The blanking period 316 may overlap the readoutperiod 302.

FIGS. 6A and 6B illustrate processes for recording an image frame.Multiple image frames may be strung together to generate a video stream.A single image frame may include data from multiple exposure frames,wherein an exposure frame is the data sensed by a pixel array subsequentto an emission of electromagnetic radiation. FIG. 6A illustrates atraditional process that is typically implemented with a color imagesensor having a color filter array (CFA) for filtering out certainwavelengths of light per pixel. FIG. 6B is a process that is disclosedherein and can be implemented with a monochromatic “color agnostic”image sensor that is receptive to all wavelengths of electromagneticradiation.

The process illustrated in FIG. 6A occurs from time t(0) to time t(1).The process begins with a white light emission 602 and sensing whitelight 604. The image is processed and displayed at 606 based on thesensing at 604.

The process illustrated in FIG. 6B occurs from time t(0) to time t(1).The process begins with an emission of green light 612 and sensingreflected electromagnetic radiation 614 subsequent to the emission ofgreen light 612. The process continues with an emission of red light 616and sensing reflected electromagnetic radiation 618 subsequent to theemission of red light 616. The process continues with an emission ofblue light 620 and sensing reflected electromagnetic radiation 622subsequent to the emission of blue light 620. The process continues withone or more emissions of a fluorescence excitation wavelengths 624 andsensing reflected electromagnetic energy 626 subsequent to each of theone or more emissions of fluorescence excitation wavelengths ofelectromagnetic radiation 624. The image is processed and displayed at628 based on each of the sensed reflected electromagnetic energyinstances 614, 618, 622, and 626.

The process illustrated in FIG. 6B provides a higher resolution imageand provides a means for generating an RGB image that further includesfluorescence imaging data. When partitioned spectrums of light are used,(as in FIG. 6B) a sensor can be made sensitive to all wavelengths ofelectromagnetic energy. In the process illustrated in FIG. 6B, themonochromatic pixel array is instructed that it is sensingelectromagnetic energy from a predetermined partition of the fullspectrum of electromagnetic energy in each cycle. Therefore, to form animage the sensor need only be cycled with a plurality of differingpartitions from within the full spectrum of light. The final image isassembled based on the multiple cycles. Because the image from eachcolor partition frame cycle has a higher resolution (compared with a CFApixel array), the resultant image created when the partitioned lightframes are combined also has a higher resolution. In other words,because each and every pixel within the array (instead of, at most,every second pixel in a sensor with a CFA) is sensing the magnitudes ofenergy for a given pulse and a given scene, just fractions of timeapart, a higher resolution image is created for each scene.

As can be seen graphically in the embodiments illustrated in FIGS. 6Aand 6B between times t(0) and t(1), the sensor for the partitionedspectrum system in FIG. 6B has cycled at least four times for every oneof the full spectrum system in FIG. 6A. In an embodiment, a displaydevice (LCD panel) operates at 50-60 frames per second. In such anembodiment, the partitioned light system in FIG. 6B may operate at200-240 frames per second to maintain the continuity and smoothness ofthe displayed video. In other embodiments, there may be differentcapture and display frame rates. Furthermore, the average capture ratecould be any multiple of the display rate.

In an embodiment, it may be desired that not all partitions berepresented equally within the system frame rate. In other words, notall light sources have to be pulsed with the same regularity so as toemphasize and de-emphasize aspects of the recorded scene as desired bythe users. It should also be understood that non-visible and visiblepartitions of the electromagnetic spectrum may be pulsed together withina system with their respective data value being stitched into the videooutput as desired for display to a user.

An embodiment may comprise a pulse cycle pattern as follows:

-   -   i. Green pulse;    -   ii. Red pulse;    -   iii. Blue pulse;    -   iv. Green pulse;    -   v. Red pulse;    -   vi. Blue pulse;    -   vii. Fluorescence excitation pulse;    -   viii. (Repeat)

As can be seen in the example, a fluorescence excitation partition maybe pulsed at a rate differing from the rates of the other partitionpulses. This may be done to emphasize a certain aspect of the scene,with the fluorescence imaging data simply being overlaid with the otherdata in the video output to make the desired emphasis. It should benoted that the addition of a fluorescence partition on top of the RED,GREEN, and BLUE partitions does not necessarily require the serializedsystem to operate at four times the rate of a full spectrum non-serialsystem because every partition does not have to be represented equallyin the pulse pattern. As seen in the embodiment, the addition of apartition pulse that is represented less in a pulse pattern(fluorescence excitation in the above example), would result in anincrease of less than 20% of the cycling speed of the sensor toaccommodate the irregular partition sampling.

In various embodiments, the pulse cycle pattern may further include anyof the following wavelengths in any suitable order. Such wavelengths maybe particularly suited for exciting a fluorescent reagent to generatefluorescence imaging data by sensing the relaxation emission of thefluorescent reagent based on a fluorescent reagent relaxation emission:

-   -   i. 770±20 nm;    -   ii. 770±10 nm;    -   iii. 770±5 nm;    -   iv. 790±20 nm;    -   v. 790±10 nm;    -   vi. 790±5 nm;    -   vii. 795±20 nm;    -   viii. 795±10 nm;    -   ix. 795±5 nm;    -   x. 815±20 nm;    -   xi. 815±10 nm;    -   xii. 815±5 nm;    -   xiii. 770 nm to 790 nm; and/or    -   xiv. 795 nm to 815 nm.

The partition cycles may be divided so as to accommodate or approximatevarious imaging and video standards. In an embodiment, the partitioncycles may comprise pulses of electromagnetic energy in the Red, Green,and Blue spectrum as follows as illustrated best in FIGS. 7A-7D. In FIG.7A, the different light intensities have been achieved by modulating thelight pulse width or duration within the working range shown by thevertical grey dashed lines. In FIG. 7B, the different light intensitieshave been achieved by modulating the light power or the power of theelectromagnetic emitter, which may be a laser or LED emitter, butkeeping the pulse width or duration constant. FIG. 7C shows the casewhere both the light power and the light pulse width are beingmodulated, leading to greater flexibility. The partition cycles may useCyan Magenta Yellow (CMY), infrared, ultraviolet, hyperspectral, andfluorescence using a non-visible pulse source mixed with visible pulsesources and any other color space required to produce an image orapproximate a desired video standard that is currently known or yet tobe developed. It should also be understood that a system may be able toswitch between the color spaces on the fly to provide the desired imageoutput quality.

In an embodiment using color spaces Green-Blue-Green-Red (as seen inFIG. 7D) it may be desirous to pulse the luminance components more oftenthan the chrominance components because users are generally moresensitive to light magnitude differences than to light colordifferences. This principle can be exploited using a mono-chromaticsensor as illustrated in FIG. 7D. In FIG. 7D, green, which contains themost luminance information, may be pulsed more often or with moreintensity in a (G-B-G-R-G-B-G-R . . . ) scheme to obtain the luminancedata. Such a configuration would create a video stream that hasperceptively more detail, without creating and transmittingunperceivable data.

In an embodiment, duplicating the pulse of a weaker partition may beused to produce an output that has been adjusted for the weaker pulse.For example, blue laser light is considered weak relative to thesensitivity of silicon-based pixels and is difficult to produce incomparison to the red or green light, and therefore may be pulsed moreoften during a frame cycle to compensate for the weakness of the light.These additional pulses may be done serially over time or by usingmultiple lasers that simultaneously pulse to produce the desiredcompensation effect. It should be noted that by pulsing during ablanking period (time during which the sensor is not reading out thepixel array), the sensor is insensitive to differences/mismatchesbetween lasers of the same kind and simply accumulates the light for thedesired output. In another embodiment, the maximum light pulse range maybe different from frame to frame. This is shown in FIG. 7E, where thelight pulses are different from frame to frame. The sensor may be builtto be able to program different blanking times with a repeating patternof two or three or four or n frames. In FIG. 7E, four different lightpulses are illustrated, and Pulse 1 may repeat for example after Pulse 4and may have a pattern of four frames with different blanking times.This technique can be used to place the most powerful partition on thesmallest blanking time and therefore allow the weakest partition to havewider pulse on one of the next frames without the need of increasing thereadout speed. The reconstructed frame can still have a regular patternfrom frame to frame as it is constituted of many pulsed frames.

FIG. 8 is a schematic diagram of a process flow 800 to be implemented bya controller and/or monochrome image signal processor (ISP) forgenerating a video stream having RGB images with fluorescence imagingdata overlaid thereon. The process flow 800 results in images havingincreased dynamic range and spatial resolution. The image signalprocessor (ISP) chain may be assembled for the purpose of generating RGBimage sequences from raw sensor data, yielded in the presence of theG-R-G-B-Fluorescence light pulsing scheme. The process flow 800 may beapplied for checkerboard wide dynamic range with the Y-Cb-Y-Cr pulsingscheme along with additional pulses for fluorescence imaging,fluorescence imaging, and/or laser mapping or tool tracking imaging.

In the process flow 800, the first stage is concerned with makingcorrections to account for any non-idealities in the sensor technologyfor which it is most appropriate to work in the raw data domain. At thenext stage, multiple exposure frames (for example, a green exposureframe 812 a, a red-blue exposure frame 812 b, and a fluorescenceexposure frame 812 c) are buffered because each final exposure framederives data from multiple raw frames. The frame reconstruction at 814proceeds by sampling data from a current exposure frame and bufferedexposure frames (see 812 a, 812 b, and/or 812 c). The reconstructionprocess results in full color image frames in linear RGB color spacethat include fluorescence image data.

The process flow 800 includes receiving data from an image sensor at802. Sensor correction calculations are performed at 804. These sensorcorrection calculations can be used to determine statistics at 806 suchas autoexposure settings and wide dynamic range settings. The processflow 800 continues and wide dynamic range fusion is processed at 808.Wide dynamic range compression is processed at 810. The wide dynamicrange compression from 810 can be fed to generate the green exposureframe 812 a, the red-blue exposure frame 812, and/or the fluorescenceexposure frame 812 c. The process flow 800 continues and framereconstruction is processed at 814 and then color correction isprocessed at 816. The process flow 800 continues and an RGB(red-green-blue) image is converted to a YCbCr (luminance-chrominanceblue-chrominance red) image at 818. Edge enhancement is processed at 820and then the YCbCr image is converted back to an RGB image at 822.Scalars are processed at 824 and gamma is processed at 826. The video isthen exported at 828.

One implementation for performing edge enhancement 820 includesextracting luminance data from an image. The “image” as discussed hereinmay be a single exposure frame or a plurality of exposure frames thathave been combined to create an image frame. The edges of the image aredetected, and a gain factor is applied to the edge data. The extractedluminance data is then combined with the modified edge data with thegain factor applied thereto. One challenge with this approach isseparating true edge and texture information from random noise in theimage.

If the random noise in the image is enhanced, the signal to noise ratiois reduced and the perceived quality of the image is degraded.Therefore, edge enhancement 820 may include applying a threshold levelof edge enhancement only when above a threshold noise distribution.Because noise increases as a function of signal, greater edgeenhancement is desirable at higher signal levels. If the threshold isexcessively high, then large edges may become disproportionatelyenhanced with respect to small transitions and textures. This can resultin an unnatural cartoon-like image. Understanding the origin of therandom temporal noise enables the real-time prediction of the optimalplacement of the threshold. If the local signal is known in electronicunits, then the sigma of the dominance shot noise component is knownexactly because the sigma of the dominant shot noise component is equalto the square root of the mean signal.

In an embodiment, the edge enhancement 820 includes continuously varyingthe threshold pixel-by-pixel. The determination of the threshold can beguided by an indication of the expected local noise. Continuous spatialand temporal alteration of the threshold provides the most idealcompromise between noise control and the efficacy of the edgeenhancement process.

In an embodiment, the edge enhancement 820 includes extracting a pureluminance component. After the pure luminance component is extracted,there are multiple methods that can be employed to determine thelocation and amplitude of edges within the image. One example method maybe referred to as the “unsharp mask” approach. The unsharp mask approachmay be implemented in hardware or software. One other method is theCanny method, in which an edge detect operator kernel is applied to aspatially filtered version of the image. One other method is theLaplacian method, which includes detecting zero crossings in the secondorder derivative. One other method includes the SUSAN method.

FIG. 9 is a schematic diagram of a process flow 900 for applying thesuper resolution (SR) and color motion artifact correction (CMAC)processes to image data. The super resolution algorithm uses data frommultiple sequential exposure frames that are combined to generateindividual image frames with increased spatial resolution. Thegeneration of the individual image frames depends upon accurate motiondetection within local regions of the multiple exposure frames. In someimplementations, the luminance plane is the most critical plane fordetermining spatial resolution. If the luminance plane is the mostcritical plane, then only the adjacent luminance exposure frames arecombined in an embodiment. In the case of red-green-blue pulsingaccording to an R-G-B-G pulsing schedule, only adjacent green exposureframes are combined to generate the individual image frames havinghigher spatial resolution.

With respect to the discussions regarding FIG. 9, the super resolutionalgorithm is applied in the context of Y-Cb-Cr light pulsing. YCbCr is afamily of color spaces that can be used as part of the color imagepipeline in video and digital photography systems. Y′ is the luminancecomponent (may be referred to as the “luma” component) and representsthe “black-and-white” or achromatic portion of the image. Cb is theblue-difference chrominance component (may be referred to as the“chroma” component) and Cr is the red-difference chrominance component.The chrominance components represent the color information in the imageor video stream. Analog RGB image information can be converted intoluminance and chrominance digital image information because human visionhas finer spatial sensitivity to luminance (black-and-white) differencesthan chromatic (color) differences. Video and imaging systems cantherefore store and transmit chromatic information at lower resolutionand optimize perceived detail at a particular bandwidth. Y′ (with theprime notation) is distinguished from Y (without the prime notation),where Y is luminance and refers to light intensity. Y′CbCr color spacesare defined by a mathematical coordinate transformation from anassociated RGB color space. If the underlying RGB color space isabsolute, the Y′CbCr color space is an absolute color space as well.

The systems and methods disclosed herein are not limited to anyparticular pulsing scheme and can be applied to YCbCr pulsing or to RGBpulsing. The super resolution algorithm may further be applied tohyperspectral and/or fluorescence image data. In an embodiment, theendoscopic imaging system disclosed herein pulses light to generate atleast four types of captured frames. The captured exposure framesinclude a Y exposure frame that contains pure luminance information, aCb exposure frame which contains a linear sum of Y and Cb data, and a Crexposure frame which contains a linear sum of Y and Cr data. Duringframe reconstruction (i.e. color fusion). There may be one full colorimage frame in the YCbCr color space that is generated for eachluminance exposure frame at the input. The luminance data may becombined with the chrominance data from the frame prior to and the framefollowing the luminance frame. Note that given this pulsing sequence,the position of the Cb frame with respect to the Y frame ping-pongsbetween the before and after slots for alternate Y cases, as does itscomplementary Cr component. Therefore, the data from each captured Cb orCr chrominance frame may be utilized in two resultant full-color imageframes. The minimum frame latency may be provided by performing thecolor fusion process during chrominance (Cb or Cr) frame capture.

In the process flow 900, data from a sensor is input at 902. Sensorcorrection 904 is performed on the sensor data. The super resolution(SR) and color motion artifact correction (CMAC) algorithms areimplemented at 906. The SR and CMAC processes 906 may be performedwithin the camera image signal processor on raw, captured sensor data.The SR and CMAC processes can be performed at 906 immediately after alldigital sensor correction 904 processes are completed. The SR and CMACprocesses 906 can be executed before the sensor data is fused intolinear RGB or YCbCr space color images. Statistics can be exported at908 to determine the appropriate autoexposure for the image.

Further in the process flow 900, a chrominance frame 910 a and aluminance frame 910 b are constructed. The luminance frame 910 b isconstructed based on luminance exposure frames in arrival order. Thechrominance frames 910 a are constructed based on chrominance (Cb andCr) exposure frames in arrival order. The fluorescence frame 910 c isconstructed based on fluorescence exposure frames in arrival order. Thenumber of exposure frames processed by the super resolution algorithm(see 906) is an optional variable. The first-in-first-out depth of theluminance frame 910 b is normally odd and its size can be determinedbased on available processing, memory, memory-bandwidth, motiondetection precision, or acceptable latency. The color motion artifactcorrection (CMAC) process can be performed with the minimumfirst-in-first-out depth of three luminance frames 910 b and twochrominance frames 910 a for Cb and/or Cr. The super resolutionalgorithm may generate better resolution by the use of five luminanceframes 910 b.

The image data is processed to implement frame reconstruction at 912 andedge enhancement at 914. The YCbCr image is converted to an RGB image at916. Statistics on the RGB image can be exported at 918 to determineappropriate white balance. The appropriate white balance is applied at920 and entered into the color correction matric at 922. Scalars 924 andgamma 926 are determined and the video is exported out at 928. Theprocess flow 900 can be implemented in the camera image signal processorin real-time while image data is captured and received from the sensor(see 902).

FIG. 10 illustrates the shape of luminance y_(i) of pixel, and the shapeof the filtered version f_(i) of the luminance, and the shape of thedifference plane d_(i). In the unsharp mask method for detecting theedges of an image, a spatially filtered version of the luminance planemay be identified and extracted from the original image to generate adifference plane. Flat areas will have a net result of zero whiletransitions will result in a local bipolar signal having amplitudes thatscale with spatial frequency. The spatial filter can be a Gaussianfilter kernel of dimension 7×7 in one embodiment. An example Gaussianfilter, H, is shown below:

$H = {\frac{1}{140}\begin{bmatrix}1 & 1 & 2 & 2 & 2 & 1 & 1 \\1 & 2 & 2 & 4 & 2 & 2 & 1 \\2 & 2 & 4 & 8 & 4 & 2 & 2 \\2 & 4 & 8 & 16 & 8 & 4 & 2 \\2 & 2 & 4 & 8 & 4 & 2 & 2 \\1 & 2 & 2 & 4 & 2 & 1 & 1 \\1 & 1 & 2 & 2 & 2 & 1 & 1\end{bmatrix}}$

If f_(i) is the filtered version of the luminance y_(i) of pixel i,then:

f _(i)=(H)(y _(i))

The difference plane, d_(i), is defined by:

d _(i) =Y _(i) −f _(i)

The resultant difference plane is effectively a high-pass filteredversion that may be manipulated by a gain factor before being added backto the original luminance plane. The gain factor may govern the strengthof the edge enhancement.

In this particular version of an edge enhancement algorithm, the gainfactor g is the product of two positive, real components referred to asα_(i) and β, according to:

g=α _(i)·β

Therefore, the final luminance representation, Y_(i), is given by:

Y _(i) =y _(i)+α_(i) ·β·d _(i)

The α_(i) factor has a maximum of unity and its magnitude may bedetermined based on what is happening locally within the image. The βfactor is a strength adjuster that may be presented to a camera operatorto tune according to aesthetic taste.

To determine what α_(i) should be, the signal calibration may first beapplied to convert the luminance plane to electronic units. Thefollowing expression can be used to compute the calibration factor, K,if the internal sensor properties known as the conversion gain E and theanalog-to-digital converter (ADC) voltage swing, W, are known, wherein nis the number of ADC bits and G is the absolute overall linear gainapplied on the sensor. If G is in logarithm units (dB) the expressionbecomes:

$K_{G} = \frac{W}{G \cdot ɛ \cdot \left( {2^{n} - 1} \right)}$

If G is in logarithmic units (dB) the expression becomes:

$K_{G} = \frac{W}{1{0^{{G/2}0} \cdot ɛ \cdot \left( {2^{n} - 1} \right)}}$

If the sensor design parameters are unknown, K can be determinedempirically by plotting photon transfer curves of noise versus signalfor a broad range of gains. In this case, K_(G) is equal to thereciprocal of the gradient within the linear region of the graph foreach gain. Once K is known, it may be used to predict the magnitude ofthe noise expectation, σ_(i) for pixel I based on the local filteredluminance f_(i) where B is the sensor black offset at the output and cis the sensor read noise.

$\sigma_{i} = \frac{\sqrt{c^{2} + {K_{G}\left( {f_{i} - B} \right)}}}{K_{G}}$

FIG. 11 depicts an example of how α might be construed to depend uponthe modulus of d_(i). In this example, α_(i) follows a lineardependence. Other implementations could be conceived in which α_(i) isnot linear but has some other mathematical progression between zero andany positive real number. For example:

$\alpha_{i} = \begin{Bmatrix}{{\frac{\left( {{d_{i}} - {t_{1} \cdot \sigma_{i}}} \right)}{\left( {{t_{2} \cdot \sigma_{i}} - {t_{1} \cdot \sigma_{i}}} \right)}\mspace{14mu} {for}\mspace{14mu} \left( {t_{1} \cdot \sigma_{i}} \right)} < {d_{i}} < \left( {t_{2} \cdot \sigma_{i}} \right)} \\{{0.0\mspace{14mu} {for}\mspace{14mu} {d_{i}}} < \; \left( {t_{1} \cdot \sigma_{i}} \right)} \\{{1.0\mspace{14mu} {for}\mspace{20mu} {d_{i}}} > \left( {t_{2} \cdot \sigma_{i}} \right)}\end{Bmatrix}$

The transition points for α_(i), t₁ and t₂ would be tuned in accordancewith the most aesthetically pleasing result and may depend upon thefunction form of α_(i) employed.

A similar approach is to compute the noise variance instead of the sigmaand to determine α_(i) based upon the square of the difference parameterd_(i) instead of the modulus. This is beneficial for an implementationin hardware because it avoids the square root calculation.

In that case, the variance expectation;

$v_{i} = \frac{c^{2} + {K_{G}\left( {f_{i} - B} \right)}}{K_{G}^{2}}$$\alpha_{i} = \begin{Bmatrix}{{\frac{\left( {d_{i}^{2} - {w_{1} \cdot v_{i}}} \right)}{\left( {{w_{2} \cdot v_{i}} - {w_{1} \cdot v_{i}}} \right)}\mspace{14mu} {for}\mspace{14mu} \left( {w_{1} \cdot v_{i}} \right)} < d_{i}^{2} < \left( {w_{2} \cdot v_{i}} \right)} \\{{0.0\mspace{14mu} {for}\mspace{14mu} d_{i}^{2}} < \left( {w_{1} \cdot v_{i}} \right)} \\{{1.0\mspace{14mu} {for}\mspace{14mu} d_{i}^{2}} > \left( {w_{2} \cdot v_{i}} \right)}\end{Bmatrix}$

with w₁ and w₂ replacing t₁ and t₂ as the two quality tuning parameters.

In practice, the implementation of real-time square root operations anddivision operations are non-trivial. One implementation involvesmultiplying by reciprocals or using precompiled lookup tables.Multiplying by reciprocals may work well if the divisor is a constantand precompiled lookup tables may work well if the range of values inthe lookup tables is small.

Another implementation, which may be implemented in hardware, may useknowledge of the applied gain and resulting noise to modify the amountof edge enhancement on a per-frame basis instead of pixel by pixel.Complicated (division and square-root) operations will be dependent noton changing pixel values, but on differences in frame values.

In this case, the major enhance equation is:

Y _(e) =Y _(o) +D·G·(Yf _(a) −Yf _(b))

where Yf_(a) is a 7×7 gaussian blur of the image and Yf_(b) is a 3×3gaussian blur of the image.

Yf_(a)−Yf_(b) is an edge detection between a blurred version of theimage and a less blurred version of the image. This difference is gainedby the product of G and D.

G is a gain factor ranging from 0 to n, where n can be any numbergreater than 0 with a defined upper limit. D is a weighting factorranging from 0 to 1. D is generated by setting twiddling factorsd_(high) and d_(low). The equation for D is:

$D = \begin{Bmatrix}{{\frac{\left( {{{{Yf}_{a} - {Y\; f_{b}}}} - d_{low}} \right)}{\left( {d_{high} - d_{low}} \right)}\mspace{14mu} {for}\mspace{14mu} d_{low}} < {{{Yf}_{a} - {Y\; f_{b}}}} < d_{high}} \\{{0.0\mspace{14mu} {for}\mspace{20mu} {{{Yf}_{a} - {Y\; f_{b}}}}} < d_{low}} \\{{1.0\mspace{14mu} {for}\mspace{20mu} {{{Yf}_{a} - {Y\; f_{b}}}}} > d_{high}}\end{Bmatrix}$

where d_(high) and d_(low) are set in the software. d_(high) is based onthe amount of gain added to the sensor. If the gain value is low,d_(low) is low, as the gain increases, so does d_(high). As gain andd_(high) increase, the slope of D flattens out. As a result, the enhanceequation requires a greater amount of difference in the high pass filterbefore it will gain up the detected edge. Because gain adds noise, thesystem responds to high gain situations by requiring greater edgedifferentiation before enhancement. In low gain and low noise situationsthe system can interpret smaller differences as edges and enhance themappropriately.

FIG. 12 is a schematic flow chart diagram of a method 1200 for edgeenhancement of a digital image. One or more steps of the method 1200 maybe performed by a computing device such as an image signal processor, acontroller of an endoscopic imaging system, a third-party computingsystem in communication with an endoscopic imaging system, and so forth.One or more steps of the method 1200 may be executed by a component ofan endoscopic imaging system such as an emitter for emittingelectromagnetic radiation, a pixel array of an image sensor, an imagesignal processing pipeline, and so forth. Additionally, one or moresteps of the method 1200 may be performed by an operator of theendoscopic imaging system such as a human operated orcomputer-implemented operator.

The method 1200 begins and an emitter illuminates at 1202 a lightdeficient environment with electromagnetic radiation. Theelectromagnetic radiation may include visible light, infrared light,ultraviolet light, hyperspectral wavelengths of electromagneticradiation, a fluorescence excitation wavelength of electromagneticradiation, and/or a laser mapping or tool tracking pattern. The method1200 continues and a computing device continuously focuses at 1204 ascene within the light deficient environment on a pixel array of animage sensor. The image sensor may be located in a distal tip of anendoscopic imaging system. The method 1200 continues and a pixel arrayof an image sensor senses at 1206 reflected electromagnetic radiation togenerate an exposure frame comprising image data. The method 1200continues and a computing resource generates at 1208 an image framebased on one or more exposure frames captured by the pixel array. Themethod 1200 continues and a computing resource detects at 1210 texturesand/or edges within the image frame. The method 1200 continues and acomputing resource enhances at 1212 the textures and/or the edges withinthe image frame. The method 1200 continues and a computing resourceretrieves from memory at 1214 properties pertaining to the pixel arrayand the applied sensor gain. The properties may pertain to using thenoise expectation to control the application of edge enhancementprocesses. The properties may pertain to assessing an expectation forthe magnitude of noise within an image frame created by the imagesensor. The method 1200 continues and a computing resource compiles at1216 a video stream by sequentially combining a plurality of imageframes.

The method 1200 can be applied to apply edge enhancement processes to animage frame. The edge enhancement may comprise a plurality ofenhancements within the original image generated by the pixel array thatcorrespond to variations of noise due to variations in photo-signal. Thedegree of applied edge enhancement may be governed by a digital gainfactor applied to the detected edges, which depends on expected noise.The method 1200 may include creating a three-dimensional image stream bycombining the image frames of a plurality of pixel arrays disposed on aplurality of substrates that are stacked.

The method 1200 may further comprise calculating noise correction basedon a combination of Poisson statistics of photon arrival and electronicnoise arising from the pixel array and its readout electronics. Themethod 1200 may include computing the expected noise, knowing theconversion gain of each pixel within the pixel array the applied sensorgain and the voltage range of the digitizer.

The method 1200 may further include deriving an empirical determinationof the expected noise from a database of laboratory experimentsconducted for the pixel array. The method 1200 may include varying alevel of illumination and plotting the signal in digital number (DN)versus the noise is DN² and recoding them into memory. The empiricaldetermination may be repeated for a plurality of applied sensor gainsettings. It will be appreciated that the method 1200 may furtherinclude measuring a gradient within the plot. It will be appreciatedthat in an implementation, the digital gain factor may be assessedlocally for each pixel, or within a local group of pixels. In animplementation, the digital gain factor may be determined for a wholeframe, based on the applied sensor gain. In an implementation, thedigital gain factor may be derived from a comparison of an edge strengthparameter to the expected noise located near each pixel. In animplementation, the system and method may further comprise controllingthe degree of edge enhancement and involves applying the digital gainfactor to the edge strength parameter and adding the result to theluminance component of the original image.

In an implementation, the edge strength parameter may be taken to be amodulus of a difference between two spatially filtered versions of theluminance component of the original image, with different filter kernelsapplied to each. In an implementation, the edge strength parameter maybe taken to be the modulus of the difference between one spatiallyfiltered and one unfiltered version of the luminance component of theoriginal frame.

FIG. 13 is a schematic diagram of a pattern reconstruction process. Theexample pattern illustrated in FIG. 13 includes Red, Green, Blue, andFluorescence Excitation pulses of light that each last a duration of T1.In various embodiments, the pulses of light may be of the same durationor of differing durations. The Red, Green, Blue, and FluorescenceExcitation exposure frames are combined to generate an RGB image withfluorescence imaging data overlaid thereon. A single image framecomprising a red exposure frame, a green exposure frame, a blue exposureframe, and a fluorescence exposure frame requires a time period of 4*T1to be generated. The time durations shown in FIG. 13 are illustrativeonly and may vary for different implementations. In other embodiments,different pulsing schemes may be employed. For example, embodiments maybe based on the timing of each color component or frame (T1) and thereconstructed frame having a period twice that of the incoming colorframe (2×T1). Different frames within the sequence may have differentframe periods and the average capture rate could be any multiple of thefinal frame rate.

In an embodiment, the dynamic range of the system is increased byvarying the pixel sensitivities of pixels within the pixel array of theimage sensor. Some pixels may sense reflected electromagnetic radiationat a first sensitivity level, other pixels may sense reflectedelectromagnetic radiation at a second sensitivity level, and so forth.The different pixel sensitivities may be combined to increase thedynamic range provided by the pixel configuration of the image sensor.In an embodiment, adjacent pixels are set at different sensitivitiessuch that each cycle includes data produced by pixels that are more andless sensitive with respect to each other. The dynamic range isincreased when a plurality of sensitivities are recorded in a singlecycle of the pixel array. In an embodiment, wide dynamic range can beachieved by having multiple global TX, each TX firing only on adifferent set of pixels. For example, in global mode, a global TX1signal is firing a set 1 of pixels, a global TX2 signal is firing a set2 of pixel, a global TXn signal is firing a set n of pixels, and soforth.

FIGS. 14A-14C each illustrate a light source 1400 having a plurality ofemitters. The emitters include a first emitter 1402, a second emitter1404, and a third emitter 1406. Additional emitters may be included, asdiscussed further below. The emitters 1402, 1404, and 1406 may includeone or more laser emitters that emit light having different wavelengths.For example, the first emitter 1402 may emit a wavelength that isconsistent with a blue laser, the second emitter 1404 may emit awavelength that is consistent with a green laser, and the third emitter1406 may emit a wavelength that is consistent with a red laser. Forexample, the first emitter 1402 may include one or more blue lasers, thesecond emitter 1404 may include one or more green lasers, and the thirdemitter 1406 may include one or more red lasers. The emitters 1402,1404, 1406 emit laser beams toward a collection region 1408, which maybe the location of a waveguide, lens, or other optical component forcollecting and/or providing light to a waveguide, such as the jumperwaveguide 206 or lumen waveguide 210 of FIG. 2.

In an implementation, the emitters 1402, 1404, and 1406 emithyperspectral wavelengths of electromagnetic radiation. Certainhyperspectral wavelengths may pierce through tissue and enable a medicalpractitioner to “see through” tissues in the foreground to identifychemical processes, structures, compounds, biological processes, and soforth that are located behind the tissues in the foreground. Thehyperspectral wavelengths may be specifically selected to identify aspecific disease, tissue condition, biological process, chemicalprocess, type of tissue, and so forth that is known to have a certainspectral response.

In an implementation where a patient has been administered a reagent ordye to aid in the identification of certain tissues, structures,chemical reactions, biological processes, and so forth, the emitters1402, 1404, and 1406 may emit wavelength(s) for fluorescing the reagentsor dyes. Such wavelength(s) may be determined based on the reagents ordyes administered to the patient. In such an embodiment, the emittersmay need to be highly precise for emitting desired wavelength(s) tofluoresce or activate certain reagents or dyes.

In an implementation, the emitters 1402, 1404, and 1406 emit a lasermapping pattern for mapping a topology of a scene and/or for calculatingdimensions and distances between objects in the scene. In an embodiment,the endoscopic imaging system is used in conjunction with multiple toolssuch as scalpels, retractors, forceps, and so forth. In such anembodiment, each of the emitters 1402, 1404, and 1406 may emit a lasermapping pattern such that a laser mapping pattern is projected on toeach tool individually. In such an embodiment, the laser mapping datafor each of the tools can be analyzed to identify distances between thetools and other objects in the scene.

In the embodiment of FIG. 14B, the emitters 1402, 1404, 1406 eachdeliver laser light to the collection region 1408 at different angles.The variation in angle can lead to variations where electromagneticenergy is located in an output waveguide. For example, if the lightpasses immediately into a fiber bundle (glass or plastic) at thecollection region 1408, the varying angles may cause different amountsof light to enter different fibers. For example, the angle may result inintensity variations across the collection region 1408. Furthermore,light from the different emitters may not be homogenously mixed so somefibers may receive different amounts of light of different colors.Variation in the color or intensity of light in different fibers canlead to non-optimal illumination of a scene. For example, variations indelivered light or light intensities may result at the scene andcaptured images.

In one embodiment, an intervening optical element may be placed betweena fiber bundle and the emitters 1402, 1404, 1406 to mix the differentcolors (wavelengths) of light before entry into the fibers or otherwaveguide. Example intervening optical elements include a diffuser,mixing rod, one or more lenses, or other optical components that mix thelight so that a given fiber receive a same amount of each color(wavelength). For example, each fiber in the fiber bundle may have asame color. This mixing may lead to the same color in each fiber butmay, in some embodiments, still result in different total brightnessdelivered to different fibers. In one embodiment, the interveningoptical element may also spread out or even out the light over thecollection region so that each fiber carries the same total amount oflight (e.g., the light may be spread out in a top hat profile). Adiffuser or mixing rod may lead to loss of light.

Although the collection region 1408 is represented as a physicalcomponent in FIG. 14A, the collection region 1408 may simply be a regionwhere light from the emitters 1402, 1404, and 1406 is delivered. In somecases, the collection region 1408 may include an optical component suchas a diffuser, mixing rod, lens, or any other intervening opticalcomponent between the emitters 1402, 1404, 1406 and an output waveguide.

FIG. 14C illustrates an embodiment of a light source 1400 with emitters1402, 1404, 1406 that provide light to the collection region 1408 at thesame or substantially same angle. The light is provided at an anglesubstantially perpendicular to the collection region 1408. The lightsource 1400 includes a plurality of dichroic mirrors including a firstdichroic mirror 1410, a second dichroic mirror 1412, and a thirddichroic mirror 1414. The dichroic mirrors 1410, 1412, 1414 includemirrors that reflect a first wavelength of light but transmit (or aretransparent to) a second wavelength of light. For example, the thirddichroic mirror 1414 may reflect blue laser light provided by the thirdemitter, while being transparent to the red and green light provided bythe first emitter 1402 and the second emitter 1404, respectively. Thesecond dichroic mirror 1412 may be transparent to red light from thefirst emitter 1402, but reflective to green light from the secondemitter 1404. If other colors or wavelengths are included dichroicmirrors may be selected to reflect light corresponding to at least oneemitter and be transparent to other emitters. For example, the thirddichroic mirror 1414 reflect the light form the third emitter 1406 butis to emitters “behind” it, such as the first emitter 1402 and thesecond emitter 1404. In embodiments where tens or hundreds of emittersare present, each dichroic mirror may be reflective to a correspondingemitter and emitters in front of it while being transparent to emittersbehind it. This may allow for tens or hundreds of emitters to emitelectromagnetic energy to the collection region 1408 at a substantiallysame angle.

Because the dichroic mirrors allow other wavelengths to transmit or passthrough, each of the wavelengths may arrive at the collection region1408 from a same angle and/or with the same center or focal point.Providing light from the same angle and/or same focal/center point cansignificantly improve reception and color mixing at the collectionregion 1408. For example, a specific fiber may receive the differentcolors in the same proportions they were transmitted/reflected by theemitters 1402, 1404, 1406 and mirrors 1410, 1412, 1414. Light mixing maybe significantly improved at the collection region compared to theembodiment of FIG. 14B. In one embodiment, any optical componentsdiscussed herein may be used at the collection region 1408 to collectlight prior to providing it to a fiber or fiber bundle.

FIG. 14C illustrates an embodiment of a light source 1400 with emitters1402, 1404, 1406 that also provide light to the collection region 1408at the same or substantially same angle. However, the light incident onthe collection region 1408 is offset from being perpendicular. Angle1416 indicates the angle offset from perpendicular. In one embodiment,the laser emitters 1402, 1404, 1406 may have cross sectional intensityprofiles that are Gaussian. As discussed previously, improveddistribution of light energy between fibers may be accomplished bycreating a more flat or top-hat shaped intensity profile. In oneembodiment, as the angle 1416 is increased, the intensity across thecollection region 1408 approaches a top hat profile. For example, atop-hat profile may be approximated even with a non-flat output beam byincreasing the angle 1416 until the profile is sufficiently flat. Thetop hat profile may also be accomplished using one or more lenses,diffusers, mixing rods, or any other intervening optical componentbetween the emitters 1402, 1404, 1406 and an output waveguide, fiber, orfiber optic bundle.

FIG. 15 is a schematic diagram illustrating a single optical fiber 1502outputting via a diffuser 1504 at an output. In one embodiment, theoptical fiber 1502 has a diameter of 500 microns, a numerical apertureof 0.65, and emits a light cone 1506 of about 70 or 80 degrees without adiffuser 1504. With the diffuser 1504, the light cone 1506 may have anangle of about 110 or 120 degrees. The light cone 1506 may be a majorityof where all light goes and is evenly distributed. The diffuser 1504 mayallow for more even distribution of electromagnetic energy of a sceneobserved by an image sensor.

In one embodiment, the lumen waveguide 210 includes a single plastic orglass optical fiber of about 500 microns. The plastic fiber may be lowcost, but the width may allow the fiber to carry a sufficient amount oflight to a scene, with coupling, diffusion, or other losses. Forexample, smaller fibers may not be able to carry as much light or poweras a larger fiber. The lumen waveguide 210 may include a single or aplurality of optical fibers. The lumen waveguide 210 may receive lightdirectly from the light source or via a jumper waveguide. A diffuser maybe used to broaden the light output 206 for a desired field of view ofthe image sensor 214 or other optical components.

Although three emitters are shown in FIGS. 14A-14C, emitters numberingfrom one into the hundreds or more may be used in some embodiments. Theemitters may have different wavelengths or spectrums of light that theyemit, and which may be used to contiguously cover a desired portion ofthe electromagnetic spectrum (e.g., the visible spectrum as well asinfrared and ultraviolet spectrums). The emitters may be configured toemit visible light such as red light, green light, and blue light, andmay further be configured to emit hyperspectral emissions ofelectromagnetic radiation, fluorescence excitation wavelengths forfluorescing a reagent, and/or laser mapping patterns for calculatingparameters and distances between objects in a scene.

FIG. 16 illustrates a portion of the electromagnetic spectrum 1600divided into twenty different sub-spectrums. The number of sub-spectrumsis illustrative only. In at least one embodiment, the spectrum 1600 maybe divided into hundreds of sub-spectrums, each with a small waveband.The spectrum may extend from the infrared spectrum 1602, through thevisible spectrum 1604, and into the ultraviolet spectrum 1606. Thesub-spectrums each have a waveband 1608 that covers a portion of thespectrum 1600. Each waveband may be defined by an upper wavelength and alower wavelength.

Hyperspectral imaging includes imaging information from across theelectromagnetic spectrum 1600. A hyperspectral pulse of electromagneticradiation may include a plurality of sub-pulses spanning one or moreportions of the electromagnetic spectrum 1600 or the entirety of theelectromagnetic spectrum 1600. A hyperspectral pulse of electromagneticradiation may include a single partition of wavelengths ofelectromagnetic radiation. A resulting hyperspectral exposure frameincludes information sensed by the pixel array subsequent to ahyperspectral pulse of electromagnetic radiation. Therefore, ahyperspectral exposure frame may include data for any suitable partitionof the electromagnetic spectrum 1600 and may include multiple exposureframes for multiple partitions of the electromagnetic spectrum 1600. Inan embodiment, a hyperspectral exposure frame includes multiplehyperspectral exposure frames such that the combined hyperspectralexposure frame comprises data for the entirety of the electromagneticspectrum 1600. In an embodiment, a hyperspectral exposure frame issensed by a pixel array in response to an emission of one or more of:electromagnetic radiation having a wavelength from about 513 nm to about545 nm; from about 565 nm to about 585 nm; and/or from about 900 nm toabout 1000 nm.

In one embodiment, at least one emitter (such as a laser emitter) isincluded in a light source (such as the light sources 202, 1400) foreach sub-spectrum to provide complete and contiguous coverage of thewhole spectrum 1600. For example, a light source for providing coverageof the illustrated sub-spectrums may include at least 20 differentemitters, at least one for each sub-spectrum. In one embodiment, eachemitter covers a spectrum covering 40 nanometers. For example, oneemitter may emit light within a waveband from 500 nm to 540 nm whileanother emitter may emit light within a waveband from 540 nm to 580 nm.In another embodiment, emitters may cover other sizes of wavebands,depending on the types of emitters available or the imaging needs. Forexample, a plurality of emitters may include a first emitter that coversa waveband from 500 to 540 nm, a second emitter that covers a wavebandfrom 540 nm to 640 nm, and a third emitter that covers a waveband from640 nm to 650 nm. Each emitter may cover a different slice of theelectromagnetic spectrum ranging from far infrared, mid infrared, nearinfrared, visible light, near ultraviolet and/or extreme ultraviolet. Insome cases, a plurality of emitters of the same type or wavelength maybe included to provide sufficient output power for imaging. The numberof emitters needed for a specific waveband may depend on the sensitivityof a monochrome sensor to the waveband and/or the power outputcapability of emitters in that waveband.

The waveband widths and coverage provided by the emitters may beselected to provide any desired combination of spectrums. For example,contiguous coverage of a spectrum using very small waveband widths(e.g., 10 nm or less) may allow for highly selective hyperspectraland/or fluorescence imaging. The waveband widths may allow forselectively emitting the excitation wavelength(s) for one or moreparticular fluorescent reagents. Additionally, the waveband widths mayallow for selectively emitting certain partitions of hyperspectralelectromagnetic radiation for identifying specific structures, chemicalprocesses, tissues, biological processes, and so forth. Because thewavelengths come from emitters which can be selectively activated,extreme flexibility for fluorescing one or more specific fluorescentreagents during an examination can be achieved. Additionally, extremeflexibility for identifying one or more objects or processes by way ofhyperspectral imaging can be achieved. Thus, much more fluorescenceand/or hyperspectral information may be achieved in less time and withina single examination which would have required multiple examinations,delays because of the administration of dyes or stains, or the like.

FIG. 17 is a schematic diagram illustrating a timing diagram 1700 foremission and readout for generating an image. The solid line representsreadout (peaks 1702) and blanking periods (valleys) for capturing aseries of exposure frames 1704-1714. The series of exposure frames1704-1714 may include a repeating series of exposure frames which may beused for generating laser mapping, hyperspectral, and/or fluorescencedata that may be overlaid on an RGB video stream. In an embodiment, asingle image frame comprises information from multiple exposure frames,wherein one exposure frame includes red image data, another exposureframe includes green image data, and another exposure frame includesblue image data. Additionally, the single image frame may include one ormore of hyperspectral image data, fluorescence image data, and lasermapping data. The multiple exposure frames are combined to produce thesingle image frame. The single image frame is an RGB image withhyperspectral imaging data. The series of exposure frames include afirst exposure frame 1704, a second exposure frame 1706, a thirdexposure frame 1708, a fourth exposure frame 1710, a fifth exposureframe 1712, and an Nth exposure frame 1726.

Additionally, the hyperspectral image data, the fluorescence image data,and the laser mapping data can be used in combination to identifycritical tissues or structures and further to measure the dimensions ofthose critical tissues or structures. For example, the hyperspectralimage data may be provided to a corresponding system to identify certaincritical structures in a body such as a nerve, ureter, blood vessel,cancerous tissue, and so forth. The location and identification of thecritical structures may be received from the corresponding system andmay further be used to generate topology of the critical structuresusing the laser mapping data. For example, a corresponding systemdetermines the location of a cancerous tumor based on hyperspectralimaging data. Because the location of the cancerous tumor is known basedon the hyperspectral imaging data, the topology and distances of thecancerous tumor may then be calculated based on laser mapping data. Thisexample may also apply when a cancerous tumor or other structure isidentified based on fluorescence imaging data.

In one embodiment, each exposure frame is generated based on at leastone pulse of electromagnetic energy. The pulse of electromagnetic energyis reflected and detected by an image sensor and then read out in asubsequent readout (1702). Thus, each blanking period and readoutresults in an exposure frame for a specific spectrum of electromagneticenergy. For example, the first exposure frame 1704 may be generatedbased on a spectrum of a first one or more pulses 1716, a secondexposure frame 1706 may be generated based on a spectrum of a second oneor more pulses 1718, a third exposure frame 1708 may be generated basedon a spectrum of a third one or more pulses 1720, a fourth exposureframe 1710 may be generated based on a spectrum of a fourth one or morepulses 1722, a fifth exposure frame 1712 may be generated based on aspectrum of a fifth one or more pulses 1724, and an Nth exposure frame1726 may be generated based on a spectrum of an Nth one or more pulses1726.

The pulses 1716-1726 may include energy from a single emitter or from acombination of two or more emitters. For example, the spectrum includedin a single readout period or within the plurality of exposure frames1704-1714 may be selected for a desired examination or detection of aspecific tissue or condition. According to one embodiment, one or morepulses may include visible spectrum light for generating an RGB or blackand white image while one or more additional pulses are emitted to sensea spectral response to a hyperspectral wavelength of electromagneticradiation. For example, pulse 1716 may include red light, pulse 1718 mayinclude blue light, and pulse 1720 may include green light while theremaining pulses 1722-1726 may include wavelengths and spectrums fordetecting a specific tissue type, fluorescing a reagent, and/or mappingthe topology of the scene. As a further example, pulses for a singlereadout period include a spectrum generated from multiple differentemitters (e.g., different slices of the electromagnetic spectrum) thatcan be used to detect a specific tissue type. For example, if thecombination of wavelengths results in a pixel having a value exceedingor falling below a threshold, that pixel may be classified ascorresponding to a specific type of tissue. Each frame may be used tofurther narrow the type of tissue that is present at that pixel (e.g.,and each pixel in the image) to provide a very specific classificationof the tissue and/or a state of the tissue (diseased/healthy) based on aspectral response of the tissue and/or whether a fluorescent reagent ispresent at the tissue.

The plurality of frames 1704-1714 is shown having varying lengths inreadout periods and pulses having different lengths or intensities. Theblanking period, pulse length or intensity, or the like may be selectedbased on the sensitivity of a monochromatic sensor to the specificwavelength, the power output capability of the emitter(s), and/or thecarrying capacity of the waveguide.

In one embodiment, dual image sensors may be used to obtainthree-dimensional images or video feeds. A three-dimensional examinationmay allow for improved understanding of a three-dimensional structure ofthe examined region as well as a mapping of the different tissue ormaterial types within the region.

In an example implementation, a fluorescent reagent is provided to apatient, and the fluorescent reagent is configured to adhere tocancerous cells. The fluorescent reagent is known to fluoresce whenradiated with a specific partition of electromagnetic radiation. Therelaxation wavelength of the fluorescent reagent is also known. In theexample implementation, the patient is imaged with an endoscopic imagingsystem as discussed herein. The endoscopic imaging system pulsespartitions of red, green, and blue wavelengths of light to generate anRGB video stream of the interior of the patient's body. Additionally,the endoscopic imaging system pulses the excitation wavelength ofelectromagnetic radiation for the fluorescent reagent that wasadministered to the patient. In the example, the patient has cancerouscells and the fluorescent reagent has adhered to the cancerous cells.When the endoscopic imaging system pulses the excitation wavelength forthe fluorescent reagent, the fluorescent reagent will fluoresce and emita relaxation wavelength. If the cancerous cells are present in the scenebeing imaged by the endoscopic imaging system, then the fluorescentreagent will also be present in the scene and will emit its relaxationwavelength after fluorescing due to the emission of the excitationwavelength. The endoscopic imaging system senses the relaxationwavelength of the fluorescent reagent and thereby senses the presence ofthe fluorescent reagent in the scene. Because the fluorescent reagent isknown to adhere to cancerous cells, the presence of the fluorescentreagent further indicates the presence of cancerous cells within thescene. The endoscopic imaging system thereby identifies the location ofcancerous cells within the scene. The endoscopic imaging system mayfurther emit a laser mapping pulsing scheme for generating a topology ofthe scene and calculating dimensions for objects within the scene. Thelocation of the cancerous cells (as identified by the fluorescenceimaging data) may be combined with the topology and dimensionsinformation calculated based on the laser mapping data. Therefore, theprecise location, size, dimensions, and topology of the cancerous cellsmay be identified. This information may be provided to a medicalpractitioner to aid in excising the cancerous cells. Additionally, thisinformation may be provided to a robotic surgical system to enable thesurgical system to excise the cancerous cells.

In a further example implementation, a patient is imaged with anendoscopic imaging system to identify quantitative diagnosticinformation about the patient's tissue pathology. In the example, thepatient is suspected or known to suffer from a disease that can betracked with hyperspectral imaging to observe the progression of thedisease in the patient's tissue. The endoscopic imaging system pulsespartitions of red, green, and blue wavelengths of light to generate anRGB video stream of the interior of the patient's body. Additionally,the endoscopic imaging system pulses one or more hyperspectralwavelengths of light that permit the system to “see through” sometissues and generate imaging of the tissue that is affected by thedisease. The endoscopic imaging system senses the reflectedhyperspectral electromagnetic radiation to generate hyperspectralimaging data of the diseased tissue, and thereby identifies the locationof the diseased tissue within the patient's body. The endoscopic imagingsystem may further emit a laser mapping pulsing scheme for generating atopology of the scene and calculating dimensions of objects within thescene. The location of the diseased tissue (as identified by thehyperspectral imaging data) may be combined with the topology anddimensions information that is calculated with the laser mapping data.Therefore, the precise location, size, dimensions, and topology of thediseased tissue can be identified. This information may be provided to amedical practitioner to aid in excising, imaging, or studying thediseased tissue. Additionally, this information may be provided to arobotic surgical system to enable the surgical system to excise thediseased tissue.

FIG. 18 is a schematic diagram of an imaging system 1800 having a singlecut filter. The system 1800 includes an endoscope 1806 or other suitableimaging device having a light source 1808 for use in a light deficientenvironment. The endoscope 1806 includes an image sensor 1804 and afilter 1802 for filtering out unwanted wavelengths of light or otherelectromagnetic radiation before reaching the image sensor 1804. Thelight source 1808 transmits light that may illuminate the surface 1812in a light deficient environment such as a body cavity. The light 1810is reflected off the surface 1812 and passes through the filter 1802before hitting the image sensor 1804.

The filter 1802 may be used in an implementation where a fluorescentreagent or dye has been administered. In such an embodiment, the lightsource 1808 emits the excitation wavelength for fluorescing thefluorescent reagent or dye. Commonly, the relaxation wavelength emittedby the fluorescent reagent or dye will be of a different wavelength thanthe excitation wavelength. The filter 1802 may be selected to filter outthe excitation wavelength and permit only the relaxation wavelength topass through the filter and be sensed by the image sensor 1804.

In one embodiment, the filter 1802 is configured to filter out anexcitation wavelength of electromagnetic radiation that causes a reagentor dye to fluoresce such that only the expected relaxation wavelength ofthe fluoresced reagent or dye is permitted to pass through the filter1802 and reach the image sensor 1804. In an embodiment, the filter 1802filters out at least a fluorescent reagent excitation wavelength between770 nm and 790 nm. In an embodiment, the filter 1802 filters out atleast a fluorescent reagent excitation wavelength between 795 nm and 815nm. In an embodiment, the filter 1802 filters out at least a fluorescentreagent excitation wavelength between 770 nm and 790 nm and between 795nm and 815 nm. In these embodiments, the filter 1802 filters out theexcitation wavelength of the reagent and permits only the relaxationwavelength of the fluoresced reagent to be read by the image sensor1804. The image sensor 1804 may be a wavelength-agnostic image sensorand the filter 1802 may be configured to permit the image sensor 1804 toonly receive the relaxation wavelength of the fluoresced reagent and notreceive the emitted excitation wavelength for the reagent. The datadetermined by the image sensor 1804 may then indicate a presence of acritical body structure, tissue, biological process, or chemical processas determined by a location of the reagent or dye.

The filter 1802 may further be used in an implementation where afluorescent reagent or dye has not been administered. The filter 1802may be selected to permit wavelengths corresponding to a desiredspectral response to pass through and be read by the image sensor 1804.The image sensor 1804 may be a monochromatic image sensor such thatpixels of the captured image that exceed a threshold or fall below athreshold may be characterized as corresponding to a certain spectralresponse or fluorescence emission. The spectral response or fluorescenceemission, as determined by the pixels captured by the image sensor 1804,may indicate the presence of a certain body tissue or structure, acertain condition, a certain chemical process, and so forth.

FIG. 19 is a schematic diagram of an imaging system 1900 having multiplecut filters. The system 1900 includes an endoscope 1906 or othersuitable imaging device having a light source 1908 for use in a lightdeficient environment. The endoscope 1906 includes an image sensor 1904and two filters 1902 a, 1902 b. It should be appreciated that inalternative embodiments, the system 1900 may include any number offilters, and the number of filters and the type of filters may beselected for a certain purpose e.g., for gathering imaging informationof a particular body tissue, body condition, chemical process, and soforth. The filters 1902 a, 1902 b are configured for preventing unwantedwavelengths of light or other electromagnetic radiation from beingsensed by the image sensor 1904. The filters 1902 a, 1902 b may beconfigured to filter out unwanted wavelengths from white light or otherelectromagnetic radiation that may be emitted by the light source 1908.

Further to the disclosure with respect to FIG. 18, the filters 1902 a,1902 b may be used in an implementation where a fluorescent reagent ordye has been administered. The filters 1902 a, 1902 b may be configuredfor blocking an emitted excitation wavelength for the reagent or dye andpermitting the image sensor 1904 to only read the relaxation wavelengthof the reagent or dye. Further, the filters 1902 a, 1902 b may be usedin an implementation where a fluorescent reagent or dye has not beenadministered. In such an implementation, the filters 1902 a, 1902 b maybe selected to permit wavelengths corresponding to a desired spectralresponse to pass through and be read by the image sensor 1904.

The multiple filters 1902 a, 1902 b may each be configured for filteringout a different range of wavelengths of the electromagnetic spectrum.For example, one filter may be configured for filtering out wavelengthslonger than a desired wavelength range and the additional filter may beconfigured for filtering out wavelengths shorter than the desiredwavelength range. The combination of the two or more filters may resultin only a certain wavelength or band of wavelengths being read by theimage sensor 1904.

In an embodiment, the filters 1902 a, 1902 b are customized such thatelectromagnetic radiation between 513 nm and 545 nm contacts the imagesensor 1904. In an embodiment, the filters 1902 a, 1902 b are customizedsuch that electromagnetic radiation between 565 nm and 585 nm contactsthe image sensor 1904. In an embodiment, the filters 1902 a, 1902 b arecustomized such that electromagnetic radiation between 900 nm and 1000nm contacts the image sensor 1904. In an embodiment, the filters 1902 a,1902 b are customized such that electromagnetic radiation between 425 nmand 475 nm contacts the image sensor 1904. In an embodiment, the filters1902 a, 1902 b are customized such that electromagnetic radiationbetween 520 nm and 545 nm contacts the image sensor 1904. In anembodiment, the filters 1902 a, 1902 b are customized such thatelectromagnetic radiation between 625 nm and 645 nm contacts the imagesensor 1904. In an embodiment, the filters 1902 a, 1902 b are customizedsuch that electromagnetic radiation between 760 nm and 795 nm contactsthe image sensor 1904. In an embodiment, the filters 1902 a, 1902 b arecustomized such that electromagnetic radiation between 795 nm and 815 nmcontacts the image sensor 1904. In an embodiment, the filters 1902 a,1902 b are customized such that electromagnetic radiation between 370 nmand 420 nm contacts the image sensor 1904. In an embodiment, the filters1902 a, 1902 b are customized such that electromagnetic radiationbetween 600 nm and 670 nm contacts the image sensor 1904. In anembodiment, the filters 1902 a, 1902 b are configured for permittingonly a certain fluorescence relaxation emission to pass through thefilters 1902 a, 1902 b and contact the image sensor 1904. In anembodiment, a first filter blocks electromagnetic radiation having awavelength from about 770 nm to about 790 nm, and a second filter blockselectromagnetic radiation having a wavelength from about 795 nm to about815 nm.

In an embodiment, the system 1900 includes multiple image sensors 1904and may particularly include two image sensors for use in generating athree-dimensional image. The image sensor(s) 1904 may becolor/wavelength agnostic and configured for reading any wavelength ofelectromagnetic radiation that is reflected off the surface 1912. In anembodiment, the image sensors 1904 are each color dependent orwavelength dependent and configured for reading electromagneticradiation of a particular wavelength that is reflected off the surface1912 and back to the image sensors 1904. Alternatively, the image sensor1904 may include a single image sensor with a plurality of differentpixel sensors configured for reading different wavelengths or colors oflight, such as a Bayer filter color filter array. Alternatively, theimage sensor 1904 may include one or more color agnostic image sensorsthat may be configured for reading different wavelengths ofelectromagnetic radiation according to a pulsing schedule such as thoseillustrated in FIGS. 5-7E, for example.

FIGS. 20A and 20B illustrate a perspective view and a side view,respectively, of an implementation of an imaging sensor 2000 having aplurality of pixel arrays for producing a three-dimensional image. Thethree-dimensional image sensor may be built on a plurality of substratesand may comprise the plurality of pixel arrays and other associatedcircuitry, wherein a plurality of pixel columns 2004 a forming the firstpixel array and a plurality of pixel columns 2004 b forming a secondpixel array are located on respective substrates 2002 a and 2002 b,respectively, and a plurality of circuit columns 2008 a and 2008 b arelocated on a separate substrate 2006. Also illustrated are theelectrical connections and communications between columns of pixels toassociated or corresponding column of circuitry.

The plurality of pixel arrays may sense information simultaneously andthe information from the plurality of pixel arrays may be combined togenerate a three-dimensional image. In an embodiment, an endoscopicimaging system includes two or more pixel arrays that can be deployed togenerate three-dimensional imaging. The endoscopic imaging system mayinclude an emitter for emitting pulses of electromagnetic radiationduring a blanking period of the pixel arrays. The pixel arrays may besynced such that the optical black pixels are read (i.e., the blankingperiod occurs) at the same time for the two or more pixel arrays. Theemitter may emit pulses of electromagnetic radiation for charging eachof the two or more pixel arrays. The two or more pixel arrays may readtheir respective charged pixels at the same time such that the readoutperiods for the two or more pixel arrays occur at the same time or atapproximately the same time. In an embodiment, the endoscopic imagingsystem includes multiple emitters that are each individual synced withone or more pixel arrays of a plurality of pixel arrays. Informationfrom a plurality of pixel arrays may be combined to generatethree-dimensional image frames and video streams.

FIGS. 21A and 21B illustrate a perspective view and a side view,respectively, of an implementation of a monolithic sensor 2100 having aplurality of pixel arrays for producing a three-dimensional image inaccordance with the teachings and principles of the disclosure. Such animplementation may be desirable for three-dimensional image capture,wherein the two-pixel arrays 2102 and 2104 may be offset during use. Inanother implementation, a first pixel array 2102 and a second pixelarray 2104 may be dedicated to receiving a predetermined range of wavelengths of electromagnetic radiation, wherein the first pixel array isdedicated to a different range of wavelength electromagnetic radiationthan the second pixel array.

FIGS. 22A and 22B illustrate a perspective view and a side view,respectively, of an implementation of an imaging sensor 2200 built on aplurality of substrates. As illustrated, a plurality of pixel columns2204 forming the pixel array are located on the first substrate 2202 anda plurality of circuit columns 2208 are located on a second substrate2206. Also illustrated in the figure are the electrical connection andcommunication between one column of pixels to its associated orcorresponding column of circuitry. In one implementation, an imagesensor, which might otherwise be manufactured with its pixel array andsupporting circuitry on a single, monolithic substrate/chip, may havethe pixel array separated from all or a majority of the supportingcircuitry. The disclosure may use at least two substrates/chips, whichwill be stacked together using three-dimensional stacking technology.The first 2202 of the two substrates/chips may be processed using animage CMOS process. The first substrate/chip 2202 may be comprisedeither of a pixel array exclusively or a pixel array surrounded bylimited circuitry. The second or subsequent substrate/chip 2206 may beprocessed using any process and does not have to be from an image CMOSprocess. The second substrate/chip 2206 may be, but is not limited to, ahighly dense digital process to integrate a variety and number offunctions in a very limited space or area on the substrate/chip, or amixed-mode or analog process to integrate for example precise analogfunctions, or a RF process to implement wireless capability, or MEMS(Micro-Electro-Mechanical Systems) to integrate MEMS devices. The imageCMOS substrate/chip 2202 may be stacked with the second or subsequentsubstrate/chip 2206 using any three-dimensional technique. The secondsubstrate/chip 2206 may support most, or a majority, of the circuitrythat would have otherwise been implemented in the first image CMOS chip2202 (if implemented on a monolithic substrate/chip) as peripheralcircuits and therefore have increased the overall system area whilekeeping the pixel array size constant and optimized to the fullestextent possible. The electrical connection between the twosubstrates/chips may be done through interconnects, which may be wirebonds, bump and/or TSV (Through Silicon Via).

It will be appreciated that the teachings and principles of thedisclosure may be used in a reusable device platform, a limited usedevice platform, a re-posable use device platform, or a singleuse/disposable device platform without departing from the scope of thedisclosure. It will be appreciated that in a re-usable device platforman end-user is responsible for cleaning and sterilization of the device.In a limited use device platform, the device can be used for somespecified amount of times before becoming inoperable. Typical new deviceis delivered sterile with additional uses requiring the end-user toclean and sterilize before additional uses. In a re-posable use deviceplatform, a third-party may reprocess the device (e.g., cleans, packagesand sterilizes) a single-use device for additional uses at a lower costthan a new unit. In a single use/disposable device platform a device isprovided sterile to the operating room and used only once before beingdisposed of.

EXAMPLES

The following examples pertain to preferred features of furtherembodiments:

Example 1 is a method. The method includes actuating an emitter to emita plurality of pulses of electromagnetic radiation and sensing reflectedelectromagnetic radiation resulting from the plurality of pulses ofelectromagnetic radiation with a pixel array of an image sensor togenerate a plurality of exposure frames. The method includes applyingedge enhancement to edges within an exposure frame of the plurality ofexposure frames. The method is such that at least a portion of theplurality of pulses of electromagnetic radiation emitted by the emittercomprises one or more of electromagnetic radiation having a wavelengthfrom about 770 nm to about 790 nm.

Example 2 is a method as in Example 1, further comprising: detecting theedges within the exposure frame; retrieving from memory a knownconversion gain and an applied sensor gain for the pixel array;calculating a threshold magnitude of noise acceptable in the exposureframe based on the known conversion gain and the applied sensor gain forthe pixel array; and adjusting a magnitude of the applied edgeenhancement based on the threshold magnitude of noise acceptable in theexposure frame.

Example 3 is a method as in any of Examples 1-2, wherein applying theedge enhancement to the edges within the exposure frame comprises:extracting luminance data from the exposure frame; detecting the edgeswithin the exposure frame; applying a gain factor to the detected edgeswithin the image frame to generate modified edge data; and merging theluminance data and the modified edge data.

Example 4 is a method as in any of Examples 1-3, further comprisingcalculating expected noise for the plurality of exposure framesgenerated by the pixel array based on one or more of: a known conversiongain for each pixel within the pixel array, a known applied sensor gainfor the pixel array, or a voltage range for a digitizer of an imageprocessing system in electronic communication with the image sensor.

Example 5 is a method as in any of Examples 1-4, wherein applying theedge enhancement comprises applying the edge enhancement in response tothe exposure frame comprising more than a threshold magnitude of noise.

Example 6 is a method as in any of Examples 1-5, wherein applying theedge enhancement comprises applying the edge enhancement on a per-pixelbasis in response to a pixel comprising more than a threshold magnitudeof noise, and wherein the method further comprises determining aper-pixel threshold magnitude of noise for a plurality of pixels in thepixel array based on expected local noise.

Example 7 is a method as in any of Examples 1-6, further comprisingdetecting the edges within the exposure frame by: applying a spatialfilter to the exposure frame, wherein the spatial filter is a Gaussianfilter; extracting a luminance plane from the exposure frame; generatinga difference plane by subtracting the spatially filtered version of theexposure frame from the luminance plane; and detecting the edges byidentifying local bipolar signals in the difference plane havingamplitudes that scale with spatial frequency.

Example 8 is a method as in any of Examples 1-7, further comprisingdetecting the edges within the exposure frame by: applying a spatialfilter to the exposure frame, wherein the spatial filter is a Gaussianfilter; and applying an edge detect operator kernel to the spatiallyfiltered version of the exposure frame.

Example 9 is a method as in any of Examples 1-8, further comprisingcalculating a gain factor for governing a magnitude of the edgeenhancement applied to the edges within the exposure frame, whereincalculating the gain factor comprises calculating based on: voltageswing of an analog-to-digital converter (ADC) in electroniccommunication with the image sensor; a known conversion gain for thepixel array; an absolute overall linear gain applied to the imagesensor; and a strength adjuster setting received from a user.

Example 10 is a method as in any of Examples 1-9, further comprisingcalculating a gain factor for governing a magnitude of the edgeenhancement applied to the edges within the exposure frame, whereincalculating the gain factor comprises: plotting a gain graph by plottingphoton transfer curves of noise versus signal for a range of potentialgains; identifying a calibration factor equal to the reciprocal of agradient within a linear region of the gain graph; predicting amagnitude of noise expectation based on the calibration factor; andcalculating the gain factor based on the predicted magnitude of noiseexpectation and a strength adjust setting received from a user.

Example 11 is a method as in any of Examples 1-10, wherein sensing thereflected electromagnetic radiation comprises sensing during a readoutperiod of the pixel array, wherein the readout period is a duration oftime when active pixels in the pixel array are read.

Example 12 is a method as in any of Examples 1-11, wherein actuating theemitter comprises actuating the emitter to emit, during a pulseduration, a plurality of sub-pulses of electromagnetic radiation havinga sub-duration shorter than the pulse duration.

Example 13 is a method as in any of Examples 1-12, wherein actuating theemitter comprises actuating the emitter to emit two or more wavelengthssimultaneously as a single pulse or a single sub-pulse.

Example 14 is a method as in any of Examples 1-13, wherein sensing thereflected electromagnetic radiation comprises generating a fluorescenceexposure frame, and wherein the method further comprises providing thefluorescence exposure frame to a corresponding system that determines alocation of a critical tissue structure within a scene based on thefluorescence exposure frame.

Example 15 is a method as in any of Examples 1-14, further comprising:receiving the location of the critical tissue structure from thecorresponding system; generating an overlay frame comprising thelocation of the critical tissue structure; and combining the overlayframe with a color image frame depicting the scene to indicate thelocation of the critical tissue structure within the scene.

Example 16 is a method as in any of Examples 1-15, wherein the criticaltissue structure comprises one or more of a nerve, a ureter, a bloodvessel, an artery, a blood flow, or a tumor.

Example 17 is a method as in any of Examples 1-16, further comprisingsynchronizing timing of the plurality of pulses of electromagneticradiation to be emitted during a blanking period of the image sensor,wherein the blanking period corresponds to a time between a readout of alast row of active pixels in the pixel array and a beginning of a nextsubsequent readout of active pixels in the pixel array.

Example 18 is a method as in any of Examples 1-17, wherein sensing thereflected electromagnetic radiation comprises sensing with a first pixelarray and a second pixel array such that a three-dimensional image canbe generated based on the sensed reflected electromagnetic radiation.

Example 19 is a method as in any of Examples 1-18, wherein actuating theemitter comprises actuating the emitter to emit a sequence of pulses ofelectromagnetic radiation repeatedly sufficient for generating a videostream comprising a plurality of image frames, wherein each image framein the video stream comprises data from a plurality of exposure frames,and wherein each of the exposure frames corresponds to a pulse ofelectromagnetic radiation.

Example 20 is a method as in any of Examples 1-19, wherein at least aportion of the plurality of pulses of electromagnetic radiation emittedby the emitter is an excitation wavelength for fluorescing a reagent,and wherein at least a portion of the reflected electromagneticradiation sensed by the pixel array is a relaxation wavelength of thereagent.

Example 21 is a system. The system includes an emitter for emitting aplurality of pulses of electromagnetic radiation. The system includes animage sensor comprising a pixel array for sensing reflectedelectromagnetic radiation to generate a plurality of exposure frames.The system includes one or more processors configurable to executeinstructions stored in non-transitory computer readable storage media,the instructions comprising applying edge enhancement to edges within anexposure frame of the plurality of exposure frames. The system is suchthat at least a portion of the pulses of electromagnetic radiationemitted by the emitter comprises one or more of: electromagneticradiation having a wavelength from about 770 nm to about 790 nm.

Example 22 is a system as in Example 21, wherein the instructionsfurther comprise: detecting the edges within the exposure frame;retrieving from memory a known conversion gain and an applied sensorgain for the pixel array; calculating a threshold magnitude of noiseacceptable in the exposure frame based on the known conversion gain andthe applied sensor gain for the pixel array; and adjusting a magnitudeof the applied edge enhancement based on the threshold magnitude ofnoise acceptable in the exposure frame.

Example 23 is a system as in any of Examples 21-22, wherein theinstructions are such that applying the edge enhancement to the edgeswithin the exposure frame comprises: extracting luminance data from theexposure frame; detecting the edges within the exposure frame; applyinga gain factor to the detected edges within the image frame to generatemodified edge data; and merging the luminance data and the modified edgedata.

Example 24 is a system as in any of Examples 21-23, wherein theinstructions further comprise calculating expected noise for theplurality of exposure frames generated by the pixel array based on oneor more of: a known conversion gain for each pixel within the pixelarray, a known applied sensor gain for the pixel array, or a voltagerange for a digitizer of an image processing system in electroniccommunication with the image sensor.

Example 25 is a system as in any of Examples 21-24, wherein at least aportion of the pulses of electromagnetic radiation emitted by theemitter results in a fluorescence exposure frame created by the imagesensor, and wherein the instructions further comprise providing thefluorescence exposure frame to a corresponding system that determines alocation of a critical tissue structure within a scene based on thefluorescence exposure frame.

Example 26 is a system as in any of Examples 21-25, wherein theinstructions further comprise: receiving the location of the criticaltissue structure from the corresponding system; generating an overlayframe comprising the location of the critical tissue structure; andcombining the overlay frame with a color image frame depicting the sceneto indicate the location of the critical tissue structure within thescene.

Example 27 is a system as in any of Examples 21-26, wherein the criticaltissue structure comprises one or more of a nerve, a ureter, a bloodvessel, an artery, a blood flow, or a tumor.

Example 28 is a system as in any of Examples 21-27, further comprising afilter that filters electromagnetic radiation having a wavelength fromabout 770 nm to about 790 nm.

Example 29 is a system as in any of Examples 21-28, further comprising afilter that filters electromagnetic radiation having a wavelength fromabout 795 nm to about 815 nm.

Example 30 is a system as in any of Examples 21-29, further comprising afirst filter that filters electromagnetic radiation having a wavelengthfrom about 770 nm to about 790 nm and a second filter that filterselectromagnetic radiation having a wavelength from about 795 nm to about815 nm.

Example 31 is means for performing any of the method steps reciting inExamples 1-20.

It will be appreciated that various features disclosed herein providesignificant advantages and advancements in the art. The following claimsare exemplary of some of those features.

In the foregoing Detailed Description of the Disclosure, variousfeatures of the disclosure are grouped together in a single embodimentfor the purpose of streamlining the disclosure. This method ofdisclosure is not to be interpreted as reflecting an intention that theclaimed disclosure requires more features than are expressly recited ineach claim. Rather, inventive aspects lie in less than all features of asingle foregoing disclosed embodiment.

It is to be understood that any features of the above-describedarrangements, examples, and embodiments may be combined in a singleembodiment comprising a combination of features taken from any of thedisclosed arrangements, examples, and embodiments.

It is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the disclosure.Numerous modifications and alternative arrangements may be devised bythose skilled in the art without departing from the spirit and scope ofthe disclosure and the appended claims are intended to cover suchmodifications and arrangements.

Thus, while the disclosure has been shown in the drawings and describedabove with particularity and detail, it will be apparent to those ofordinary skill in the art that numerous modifications, including, butnot limited to, variations in size, materials, shape, form, function andmanner of operation, assembly and use may be made without departing fromthe principles and concepts set forth herein.

Further, where appropriate, functions described herein can be performedin one or more of: hardware, software, firmware, digital components, oranalog components. For example, one or more application specificintegrated circuits (ASICs) or field programmable gate arrays (FPGAs)can be programmed to carry out one or more of the systems and proceduresdescribed herein. Certain terms are used throughout the followingdescription and claims to refer to particular system components. As oneskilled in the art will appreciate, components may be referred to bydifferent names. This document does not intend to distinguish betweencomponents that differ in name, but not function.

The foregoing description has been presented for the purposes ofillustration and description. It is not intended to be exhaustive or tolimit the disclosure to the precise form disclosed. Many modificationsand variations are possible in light of the above teaching. Further, itshould be noted that any or all the aforementioned alternateimplementations may be used in any combination desired to formadditional hybrid implementations of the disclosure.

Further, although specific implementations of the disclosure have beendescribed and illustrated, the disclosure is not to be limited to thespecific forms or arrangements of parts so described and illustrated.The scope of the disclosure is to be defined by the claims appendedhereto, any future claims submitted here and in different applications,and their equivalents.

What is claimed is:
 1. A method comprising: actuating an emitter to emita plurality of pulses of electromagnetic radiation; sensing reflectedelectromagnetic radiation resulting from the plurality of pulses ofelectromagnetic radiation with a pixel array of an image sensor togenerate a plurality of exposure frames; and applying edge enhancementto edges within an exposure frame of the plurality of exposure frames;wherein at least a portion of the plurality of pulses of electromagneticradiation emitted by the emitter comprises electromagnetic radiationhaving a wavelength from about 770 nm to about 790 nm.
 2. The method ofclaim 1, further comprising: detecting the edges within the exposureframe; retrieving from memory a known conversion gain and an appliedsensor gain for the pixel array; calculating a threshold magnitude ofnoise acceptable in the exposure frame based on the known conversiongain and the applied sensor gain for the pixel array; and adjusting amagnitude of the applied edge enhancement based on the thresholdmagnitude of noise acceptable in the exposure frame.
 3. The method ofclaim 1, wherein applying the edge enhancement to the edges within theexposure frame comprises: extracting luminance data from the exposureframe; detecting the edges within the exposure frame; applying a gainfactor to the detected edges within the image frame to generate modifiededge data; and merging the luminance data and the modified edge data. 4.The method of claim 1, further comprising calculating expected noise forthe plurality of exposure frames generated by the pixel array based onone or more of: a known conversion gain for each pixel within the pixelarray, a known applied sensor gain for the pixel array, or a voltagerange for a digitizer of an image processing system in electroniccommunication with the image sensor.
 5. The method of claim 1, whereinapplying the edge enhancement comprises applying the edge enhancement inresponse to the exposure frame comprising more than a thresholdmagnitude of noise.
 6. The method of claim 1, wherein applying the edgeenhancement comprises applying the edge enhancement on a per-pixel basisin response to a pixel comprising more than a threshold magnitude ofnoise, and wherein the method further comprises determining a per-pixelthreshold magnitude of noise for a plurality of pixels in the pixelarray based on expected local noise.
 7. The method of claim 1, furthercomprising detecting the edges within the exposure frame by: applying aspatial filter to the exposure frame, wherein the spatial filter is aGaussian filter; extracting a luminance plane from the exposure frame;generating a difference plane by subtracting the spatially filteredversion of the exposure frame from the luminance plane; and detectingthe edges by identifying local bipolar signals in the difference planehaving amplitudes that scale with spatial frequency.
 8. The method ofclaim 1, further comprising detecting the edges within the exposureframe by: applying a spatial filter to the exposure frame, wherein thespatial filter is a Gaussian filter; and applying an edge detectoperator kernel to the spatially filtered version of the exposure frame.9. The method of claim 1, further comprising calculating a gain factorfor governing a magnitude of the edge enhancement applied to the edgeswithin the exposure frame, wherein calculating the gain factor comprisescalculating based on: voltage swing of an analog-to-digital converter(ADC) in electronic communication with the image sensor; a knownconversion gain for the pixel array; an absolute overall linear gainapplied to the image sensor; and a strength adjuster setting receivedfrom a user.
 10. The method of claim 1, further comprising calculating again factor for governing a magnitude of the edge enhancement applied tothe edges within the exposure frame, wherein calculating the gain factorcomprises: plotting a gain graph by plotting photon transfer curves ofnoise versus signal for a range of potential gains; identifying acalibration factor equal to the reciprocal of a gradient within a linearregion of the gain graph; predicting a magnitude of noise expectationbased on the calibration factor; and calculating the gain factor basedon the predicted magnitude of noise expectation and a strength adjustsetting received from a user.
 11. The method of claim 1, wherein sensingthe reflected electromagnetic radiation comprises sensing during areadout period of the pixel array, wherein the readout period is aduration of time when active pixels in the pixel array are read.
 12. Themethod of claim 1, wherein actuating the emitter comprises actuating theemitter to emit, during a pulse duration, a plurality of sub-pulses ofelectromagnetic radiation having a sub-duration shorter than the pulseduration.
 13. The method of claim 1, wherein actuating the emittercomprises actuating the emitter to emit two or more wavelengthssimultaneously as a single pulse or a single sub-pulse.
 14. The methodof claim 1, wherein sensing the reflected electromagnetic radiationcomprises generating a fluorescence exposure frame in response toemission of the electromagnetic radiation having a wavelength from about770 nm to about 790 nm, and wherein the method further comprisesproviding the fluorescence exposure frame to a corresponding system thatdetermines a location of a critical tissue structure within a scenebased on the fluorescence exposure frame.
 15. The method of claim 14,further comprising: receiving the location of the critical tissuestructure from the corresponding system; generating an overlay framecomprising the location of the critical tissue structure; and combiningthe overlay frame with a color image frame depicting the scene toindicate the location of the critical tissue structure within the scene.16. The method of claim 15, wherein the critical tissue structurecomprises one or more of a nerve, a ureter, a blood vessel, an artery, ablood flow, or a tumor.
 17. The method of claim 1, further comprisingsynchronizing timing of the plurality of pulses of electromagneticradiation to be emitted during a blanking period of the image sensor,wherein the blanking period corresponds to a time between a readout of alast row of active pixels in the pixel array and a beginning of a nextsubsequent readout of active pixels in the pixel array.
 18. The methodof claim 1, wherein sensing the reflected electromagnetic radiationcomprises sensing with a first pixel array and a second pixel array suchthat a three-dimensional image can be generated based on the sensedreflected electromagnetic radiation.
 19. The method of claim 1, whereinactuating the emitter comprises actuating the emitter to emit a sequenceof pulses of electromagnetic radiation repeatedly sufficient forgenerating a video stream comprising a plurality of image frames,wherein each image frame in the video stream comprises data from aplurality of exposure frames, and wherein each of the exposure framescorresponds to a pulse of electromagnetic radiation.
 20. The method ofclaim 1, wherein at least a portion of the plurality of pulses ofelectromagnetic radiation emitted by the emitter is an excitationwavelength for fluorescing a reagent, and wherein at least a portion ofthe reflected electromagnetic radiation sensed by the pixel array is arelaxation wavelength of the reagent.
 21. A system comprising: anemitter for emitting a plurality of pulses of electromagnetic radiation;an image sensor comprising a pixel array for sensing reflectedelectromagnetic radiation to generate a plurality of exposure frames;and one or more processors configurable to execute instructions storedin non-transitory computer readable storage media, the instructionscomprising applying edge enhancement to edges within an exposure frameof the plurality of exposure frames; wherein at least a portion of thepulses of electromagnetic radiation emitted by the emitter compriseselectromagnetic radiation having a wavelength from about 770 nm to about790 nm.
 22. The system of claim 21, wherein the instructions furthercomprise: detecting the edges within the exposure frame; retrieving frommemory a known conversion gain and an applied sensor gain for the pixelarray; calculating a threshold magnitude of noise acceptable in theexposure frame based on the known conversion gain and the applied sensorgain for the pixel array; and adjusting a magnitude of the applied edgeenhancement based on the threshold magnitude of noise acceptable in theexposure frame.
 23. The system of claim 21, wherein the instructions aresuch that applying the edge enhancement to the edges within the exposureframe comprises: extracting luminance data from the exposure frame;detecting the edges within the exposure frame; applying a gain factor tothe detected edges within the image frame to generate modified edgedata; and merging the luminance data and the modified edge data.
 24. Thesystem of claim 21, wherein the instructions further comprisecalculating expected noise for the plurality of exposure framesgenerated by the pixel array based on one or more of: a known conversiongain for each pixel within the pixel array, a known applied sensor gainfor the pixel array, or a voltage range for a digitizer of an imageprocessing system in electronic communication with the image sensor. 25.The system of claim 21, wherein at least a portion of the pulses ofelectromagnetic radiation emitted by the emitter results in afluorescence exposure frame created by the image sensor, and wherein theinstructions further comprise providing the fluorescence exposure frameto a corresponding system that determines a location of a criticaltissue structure within a scene based on the fluorescence exposureframe.
 26. The system of claim 25, wherein the instructions furthercomprise: receiving the location of the critical tissue structure fromthe corresponding system; generating an overlay frame comprising thelocation of the critical tissue structure; and combining the overlayframe with a color image frame depicting the scene to indicate thelocation of the critical tissue structure within the scene.
 27. Thesystem of claim 26, wherein the critical tissue structure comprises oneor more of a nerve, a ureter, a blood vessel, an artery, a blood flow,or a tumor.
 28. The system of claim 21, further comprising a filter thatfilters electromagnetic radiation having a wavelength from about 770 nmto about 790 nm.